Chapter VIII

Data and file management fundamentals

Database fundamentals

Information security fundamentals

File fundamentals1- What is a file?

a. A file is the smallest named collection of data/information or instructions stored on a storage medium.

b. A file must have a name before being saved.c. File name must be descriptive to indicate the content of the file and must abide by the

following criteria:i. Maximum length shouldn’t exceed 255 characters

ii. Avoid prohibited characters *?”/I><:\iii. Case sensitive: “A” and “a” are different characters in the file name.

d. The file name must end with an extension that is related to the format used when the file was saved. (.txt, .doc, .gif, .xls, etc…)

e. Native file format is format used when we create the file: Example (if we use MS word to create a document then we save the document as a pdf file its native file format will be .doc and its filename extension will be .pdf)

f. File name extension cannot exceed 3 characters.g. Operating system can be set to hide the file name extension

2- Types of files: a. Program file or software file:

i. consists of software instructions designed to instruct the computer how to perform specific applications

ii. an application may consist of one or several programsiii. all program files are saved on the hard disk in a folder called “program files”

folder which is the default folder used by the operating system to store software programs including the ones that you download from the WEB.

iv. Program file can be ASCII text file that needs conversion to binary or binary executable file that don’t need any conversion.

b. Data files: i. Files that hold data/information of all types

ii. No instructions included in data files.iii. Content vary from text to document to multimedia (pictures, audio, video, etc…)

3- Physical storage model: a. Each storage medium is formatted and divided into sectors b. CD has one single track about 3 miles long: 336000 sectors of 2048 bytes each 336000 x

2048 = about 700 megabytes c. The smallest storage location is not the sector but the clusterd. A cluster is formed of several contiguous sectors.e. Operating system stores each record of a saved file in an available cluster and gives it a

flag and order number in the corresponding file.

f. Consequently, a given file has its records dispersed all over the storage mediumg. Operating system maintain a list of addresses of files in a FAT (File Allocation Table)

that serves like the occupancy board at the entrance of office buildings.h. Defragmentation utility brings same file records as close to each other as possiblei. The FAT addressing technology helps the operating system to retrieve the file when we

want them to be displayed.j. NTFS (New Technology File System) and HPFS (High Performance File System) and

IFS (Installable File System) are newer more advanced technologies than FAT which is still used because of its effectiveness.

4- File storage and retrieval (Logical storage model) a. The operating system creates a directory for each storage medium and maintain a table of

addresses for all files stored on that directoryb. The directory is considered to be the logical storage model that identifies the path to each

file thru directories and subdirectories.c. This logical storage model is like a tree metaphor that consists of:

i. Root directory: The storage medium depicted as the trunk of the tree. Example for the hard disk (C:\)

ii. Subdirectories: considered as the folders and subfolders depicted as the branches.iii. Files depicted as the leavesiv. Example: C:\electronics\computers\notebook\apple.exlv. The above example in computer store represents the path of the available apple

notebooks excel file stored in the notebook subfolder which is stored in the computer subfolder which is also stored in the electronic folder on the hard disk.

5- In the screen shot above of windows explorer:a. The folders are represented by a folder shape followed by the folder nameb. The files that are not saved in folders are listed below the folders with their file name

extensionc. The date is the date when the file was created or last time updated

d. The volume represents the actual byte count of each file that corresponds to the listed date.

6- File management software (Windows Explorer or Mac finder) allows you to manipulate files and folders in the following ways:

a. Rename: Change the name use (Save as)

b. Copy: make a copy of the file so you can paste it in another location

c. Move: You can move the file from its actual location to another and change its logical storage model accordingly.

d. Delete: Move the file to the recycle bin folder

2- MOVE/DELETE files:

a. When you move a file from one location to another all its bits stay where they were until they are overwritten by other files.

b. Only the status of the corresponding clusters will be turned from occupied to vacant so they will be used by the Operating system to store other files.

c. When you delete a file, you in fact, are moving it to the recycle bin folder where it will stay and can be retrieved as long as that folder is not emptied or overloaded.

d. File shredder is software that overwrites the old file ASCII code using random zeroes and ones.

Database fundamentals

1- What is a database? a. A database is a collection of related data files that consists of all data/information of a

business or organization.b. Database files are also called tables or relations because they are tables similar to

spreadsheet files.c. In other words Database may be defined as a collection of related files used as a

centralized homogeneous source of data/information used by many users in a business and is very flexible to allow the following procedures:

i. Collect and store dataii. Update data

iii. Organize and output dataiv. Find and analyze data

2- Data warehouse and data-mart a. If the number of files in a business or organization is too big, which is usually the case in

big businesses, then several databases will be necessary and a data warehouse is created which consists of a collection of several related databases.

b. A small data warehouse is known as a data-mart.c. Creation and manipulation of database is not possible without powerful software known

as DBMS (Database management software). MS Access is a database management system.

3- Functions of DBMS a. Helps create the database files or projectsb. Helps manipulate the database: update information, add new information delete and all

necessary operations.c. Sorts data based on given criteria.d. Provides interface between the user and the database thru 2 applications;

i. Front end application interface between the user like the forms and direct links provided by the application

ii. Back end application interacts with program and applications of the database that are used by the users.

iii. Prepare routine tasks using available data:1. Paychecks for employees2. Issue letters and labels and other promotional material.3. Tax forms 4. Client and supplier accounts5. Etc…

iv. Helps decision makers with the decision process by providing reports and statistics needed for that purpose.

v. Provides for possibility to query the database by authorized people in order to get needed information and data.

vi. Helps in enhancing data security by protecting data from intruders, attacks and all unauthorized queries.

4- Database structure: a. Field: is the building bloc of the database and its data. It is the smallest data element that

must have well defined characteristics:i. Length: how many characters and if it is fixed or variable.

ii. Type: Alpha, numeral, decimal, currency, date, etc…iii. Never store last name and first name in the same field.iv. Each part of the name must have its own field. Example the name Dr. Maya N.

Abdallah Jr. must be stored in 5 fields.v. Each data element that fits in a field is known as the field attribute.

b. Record: i. The record is a collection of related fields.

ii. If the number of fields is too big the record will be very bulky and we may need to create another record and consequently another file.

c. Table or relation i. The file in a database is known as a table or a relation.

ii. It consists of a collection of many related recordsiii. Files in the database have relationships necessary to extract all information we

need from different files.iv. Each table, regardless of its size, is composed of:

1. One record type which consists of the record template of all the labels of the record.

2. A number of record occurrences equal to the number of the population of the file

d. Database structure is depicted in the following database sample of a department store where the database is composed of 5 tables as follow: Clients, Suppliers, Employees, Inventory, Sales

e. Employees file has a sample depicted in the table below:

ID # Last name

First name

suffix Department #

Date of hire

123456 Smith Ted Sr 22 050508456789 Rogers Bill 19 022599157157 Salam Ziad Jr. 18 031608989898 Jolie Raya 22 111210

f. The record type or is the first row of the table (the red labels row)g. Each entire record (row of the table) filled of information is an occurrence.h. Each cell of the row record is a field and data in each field of the record is the attribute of

that field.i. The name Ted Smith Sr. as you see was stored in 3 fields (one for each part of the name)

and the file designer must take into consideration the longest names so that he can add the required fields that satisfy all the population of the file.

5- Keys: a. Database manipulation and data retrieval from a database will not be possible without a

key that identify data and information stored into the database. b. There are two types of keys:

i. Primary key : which is a field unique to each record (PID, SSN, ID#, etc…) database designer must be very careful when defining primary keys especially for inventory items.

ii. Secondary key : May be any other field of the file. iii. In the sample file above:

1. ID# is the primary key that is unique to each employee (it is not possible that 2 employees get the same ID# in the same business)

2. All other fields of the record type may be used as secondary keys used when needed to extract information. Example: We may use the date of hire as key to get a list of all employees that were hired in 2008 for example.

iv. Secondary keys are mostly used to get lists and reports following specific criteria presented or previously scheduled by authorities that demanded the reports and they are subject to many updating

v. Primary key, on the other hand, is normally permanent information that is not updated or rarely updated.

vi. As we may notice sometimes secondary keys are used much more than primary keys that may end up being used in operations that follow the application of secondary keys.

6- Database relations a. All modern databases are relational databases which means that all the files tables of the

database have one or more common field with other table or tables depending on the type of the relationship that may be classified under 3 types:

i. One to one: when the table has only one common field with another table

employees position

ii. One to many : One supplier supplies many products(Business uses only one supplier for a part of its products)

One to many

iii. Many to many: One supplier supplies many products and a product is supplied by many suppliers: (when many suppliers supply the same products to the same company)

Many to many

7- Data warehouse and data-mart: a. If the number of files in a business or organization is too big, which is usually the case in

big businesses, then several databases will be necessary and a data warehouse is created b. Data warehouse consists of a collection of several related databases that form a big

multidimensional database ad cover all files in multidimensional establishment.c. A small data warehouse is known as data-mart.d. They can be depicted as a cube shape where each separate cut represents a database.

8- Database operations: a. Normalization: process of eliminating redundant data which results in reducing the size

of the database.b. Selection: process of selecting from the database records that meet given criteria.

Example clients whose accounts exceed $ 5000.c. Joining table : to shrink the number of tables or files in a database we may join 2 or more

tables together to form one table.d. Data-mining: Finding hidden relationships between data in several databases of the data

warehousee. Data dictionary: represents a perfect description of the database design and all data fields

and their characteristics. f. Database schema depicts the database structure written in plain English or any other

language. It complement the data dictionary in explaining the content of the database.9- Object oriented database (OODB)

a. consists of classes of objects and subclasses or sub-objects: Example:i. Transportation: air, sea, ground- rail road, automobiles- buses, trucks, etc…

b. The most important advantage of OODB is its reusability (it can be treated like a template

10- Querying database: a. SQL (Structured Query Language) is used in forms that are converted into queries by

the DBMS. Example: grade form on CGS2100 website.i. SQL used keywords are:

1. CREATE2. DELETE3. INSERT

productssuppliers

Suppliers products Data warehous

e

4. JOIN5. SET6. SELECT7. UPDATE

ii. Example: SELECT 32” TV FROM electronics Where TV Brand = Sonyiii. SQL also allows the use of logical operators: AND, OR, NOT iv. The grade form on the course website: When you fill and submit it will be

converted into SQL to select your grade page from the database of grades.b. Query by objective:

i. Used to get lists by categories of data: Example (seafood, meat, poultry, fruit, vegetables, etc…)

ii. Used in Object Oriented Data Base (OODB) where data consists of classes of objects and subclasses or sub-objects and where the query will result in lists of data objects and sub-objects meeting selected data criteria.

11- Designing user interface a. Forms are the most used user interface they should be designed carefully to make it user

friendly as much as possible. Forms must be:b. Fields arranged in a logical orderc. Boxes areas should be clear, visible and consistent with data to filld. Provide easy samples with instructions about the filling of data.

12- OODB (Object Oriented Database)

a. Data is stored as objects that are grouped into classes and subclassesb. OODB is reusable and portable because:

i. Functions and application methods are defined with each object and can be reused by all subclasses.

ii. You only need to add your special parameters and the model will work for you if you belong to the same class activity.

iii. Example: If transportation network is an object: there are general functions and attributes that are valid for all kind of transportation classes:

1. Air transportation2. Water transportation 3. Ground transportation 4. In Ground transportation there are general functions and attribute that are

valid for all forms of ground transportation5. We don’t have to start always from scratch when building a database

iv. Another example is Grocery: meat, seafood, poultry, fruit, etc…c. Classes include data and functions that manipulate data, and lower subclasses inherit

these functions from higher classesd. OODBMS (Object Oriented Database Management System) is needed to manipulate the

OODBe. Access can manipulate all types of databases including OODB.

13- Management approach using files or database pros and cons :a. File approach: each department will create and maintain its own files

i. Strengths: 1. More security2. Limited and clear responsibility3. Close knowledge of the subject matter of data/information

ii. Weaknesses: 1. Redundancy: same record is repeated in many departments.2. Limited involvement in the general business picture

3. No or limited networking possibility4. No cooperation between all business department5. Poor quality reports and decision making information tool.

b. Database approach: i. Strengths:

1. No redundancy2. Centralized source of same information among all departments3. Networking heaven because of database server that will be able to

provide information to all clients4. Security is enhanced thru strict central policy and limited people are

manipulating the database.5. Much better quality report and customer and supplier service.

Malware and computer security

Threat to information

1- Why information system is always under attack? a. As we have illustrated in previous chapters, business executives believe that the

information they possess and use throughout their business information system is probably the most valuable asset they have.

b. Since Internet includes almost all media used to exchange and manipulate information, Corporate and government networks being de facto parts of the Internet, found themselves under permanent attack, and the Internet is the battlefield

c. Many types of attacks can be made on computer systemsi. Malware: Viruses, worms and Trojan horses

ii. Identity theftiii. Theft of personal informationiv. Unauthorized use of other’s computer

2- Origin of the threat may be attributed to the following: a. Business intelligence is the process of gathering and analyzing information about the

market and their business competitors. Counterintelligence measures may protect from this threat or at least minimize it.

b. Hackers and intruders willing to get possession of valuable information and sell it to competitors making big bucks and they always find their way using software and network vulnerabilities resulting from bugs (software holes)

c. Software bugs or security holes allow violations of information security.d. These bugs are usually dealt with by the OS provider by extracting them and using

frequent update processes to fill the holes created after their extraction.e. The update is achieved by using patches (healthy programs that replace the extracted

bugs)f. Update process usually enhance the security by using good working software patches

denying the hackers access to many of their harming tools

3- Piracy and Plagiarism a. Piracy is getting illegal possession of intellectual property such as software and make

counterfeit copies destined to be sold for very low price.b. Plagiarism involves taking credit for someone else’s intellectual property, typically a

written idea, by claiming it as your own.4- Authentication:

a. Authentication is the widely used technology to protect against intruders and attacks on information system and computer networks.

b. There are 3 authentication approaches:c. Something you know (User ID and password)

i. A password is a combination of characters known only to the user and used for authentication.

ii. A good password must have most of the following requirements:1. Strong by including words that are unrelated to your interests, and

include upper and lowercase letters, numbers, and symbols2. Unique (same password must not be used in many different accounts).3. Changed regularly (at least once every 3 months)

d. Something you have (badge, tag, etc…)i. Badges or ID card authentication, are something you may have to carry in order

to be allowed access to many restricted access placesii. Important high security areas include: Labs, computer systems, production

plants premises and equipmentiii. Simulator and training equipment, etc...

e. Biometrics- Something exclusively specific to you and unique about you : i. Biometrics authentication technology consists of scanning and measuring a

person’s unique physical features such as: 1. Fingerprints: The least expensive biometrics authentication technology.2. Retinal patterns: map and measures all vessels on the back of the retina.3. Facial characteristics4. Facial and retinal are relatively expensive technologies

5- Interior threats : a. Refers to risks and dangers from legitimate users that may harm business information

system and its network resources; they include:i. Threats to System Health and Stability

ii. Information theftiii. Employees are very serious threat by negligence or infidelity.

b. Safeguards include the use of security and usage policies which defines acceptable and unacceptable uses of computer and network resources by business employees

c. Employers are not legally responsible for errant employees behavior when using business IT resources

d. When using these resources, employees must abide by ethic rules that are widely known to everyone.

6- War driving : a. Driving through neighborhoods with a wireless notebook or handheld computer and

looking for unsecured (unprotected) Wi-Fi networks.b. Networks Use discovered access points for illegal Internet use and fraudulent Internet

personal and business transactions.7- Hacking and hackers :

a. A hacker is an extremely skilled programmer who may use his expertise to author software programs that overcome network security system and penetrate to these networks with or without user’s knowledge.

b. There are three types of hackers:i. Black hat hacker (criminal category of hackers):

1. Shrewd and very skilled programmer who designs, implement and executes hacking schemes.

2. Hacking scheme is a plan based on written hacking software that enables the hacker to access and possibly use his victim’s IT resources.

3. This act is considered a felony that results in variable levels of damage that are usually very difficult to quantify.

ii. White hat hacker: 1. Shrewd and very skilled programmer who makes legal money when

hired by establishments to test the security of their networks and information system.

2. His clients may include, without being limited to:a. Corporate and financial establishments.b. Government agencies and bodies.c. Security agencies from all over the world.

iii. Grey hat hackers: Suspicious white hat hackers8- Hacking convention and conferences

a. Hackers organize important conferences around the world every year:i. The most important is the Las Vegas – Nevada convention

ii. An equally important one is the European convention held in Athens – Greece b. Hacking material discussed during the three day program of each of these conventions

include and not limited to, the following:i. Discuss the latest hacking technologies and try them on each other.

ii. Unveil security flows they found in software that are considered very well protected by most computer experts.

iii. Present new technologies like hacking into a voting machine and into an ATM machine or how to destroy data urgently if you feel you are subject to being caught, etc…

iv. In the 2012 convention in Las Vegas - Nevada, a tricked ATM was placed in the lobby of the hotel:

1. Attendees got an email that all ATMs are not working except that one. 2. The malicious machine was set to get information about users financial

profiles. 3. It did get a lot of information before being detected by the hackers

themselves.c. The number of attendees of each of these highly organized conferences is estimated to be

between 10 000 and 15 000 that may include:i. Most skilled professionals in hacking and code breaking fields from all countries

around the world.ii. Corporates, financial and government agencies.

iii. Security agencies and agents from all around the worldiv. Computer specialists, experts and IT department employees from all kind of

companies, colleges and independent attendees.d. Attendees in general are looking to meet and recruit skilled and highly reputed hackers

that enhance their IT department performance.e. The most important meetings are considered to be f. European convention that is usually held in Athens – Greeceg. When you ask hackers: Why Do you hack? You will get a bunch of diversified answers

that may include:

i. I do it as a hobby like playing a sophisticated game

ii. My job as intelligence agent necessitates a platform gain on target networks to:1. Be able to gather secret information about competitors or suspicious

agents. 2. Ultimately, prepare for advanced intelligence and counter-intelligence

schemes that may follow in the future.iii. To innocently try a hacking scheme that I didn’t want to use and harm anybodyiv. You will never find a hacker who is able to incriminate himself and tell you: “I

hack for personal careless gain without any consideration of damages that hacking scheme may cause to hacked victims”

Malware: Malicious softwareViruses, Worms and & Trojan horses

1- Malware main agents a. Virus

i. A bad program that attaches itself to a file ii. Spreads to other files

iii. A virus delivers a destructive action called a payload.iv. A virus uses a trigger event to start its payload delivery

1. If the event is a date the malware is known as “Time bomb”2. If it is a condition or happening of an event then it is known as ”Logic

bomb”v. Types of viruses include beside the simple virus, some sophisticated malware as:

1. Polymorphic virus: change its signature each time it infects a new file but antivirus software is still able to find it thru specific tracking.

2. Multipartite virus that infects in many ways: a. Size of files change frequently.b. Much longer program loading timec. The worst and most dangerous aspect of this diversified payload

is when Hard Disk Drive reformats itself causing the system to crash and be out of use.

3. Rootkit virus: a. It is usually installed by a Trojan horse and disguised as a

legitimate system software programb. Intended to give computer control to an outside party.

4. Macro virus: uses macros (small automated programs) available in application software (EXCEL, MS WORD, etc…) to infect files and spreads to other files.

b. W orm i. It usually arrives with an email attachment

ii. Does not attach itself to other files iii. It makes copies of itself and facilitates their distribution using system

vulnerabilities and emails. iv. It replicates itself numerous times in an effort to overwhelm systems and their

networks resulting in denial of service attack (network overwhelmed with extremely high worm traffic deny access to any other email activity).

c. Trojan horse i. Unlike viruses, Trojan horses or simply Trojans behave exactly like the wooden

Trojan horse of the Greek story of the Trojan War. That is they appear to be harmless legitimate programs! While, in fact, they are not.

ii. When they run, they install programs on the computer that can be extremely harmful to the computer information system.

iii. Types of Trojans include and not limited to:1. Backdoor or Remote access Trojan : opens ports on the computer for

hacker’s access and provides hacker with commanding control of the victim’s computer system.

2. Proxy Trojan : May use the computer as a proxy server that enables it to obtain credit card and financial information to be used in illegal fraudulent activities.

3. Security killer Trojan : Designed to disable firewalls, antivirus software and anti-spyware. It usually have another destructive role beside its security mission.

4. FTP Trojan : Designed to open the FTP port without any FTP activity of your side, and enable hacker to connect to the computer system.

2- Antivirus software a. Scans files and finds malware using checksum number which is the pre-calculated sum of

all the bytes of a file.b. Calculate the actual number and compare it to the checksum saved for that same filec. If the numbers are different then a virus must have attached itself to the file.d. Antivirus software has to find out the ID of the malware so it will be able to remove it e. Malware ID can be uncovered by using the malware signature (its characteristics) and

compare it with the available list of malware signatures.f. Once it knows all about the malware, antivirus software will try to:

i. Remove the malware if possible or else ii. Quarantine it so it will not be able to harm the system

iii. Schedule it to be removed later.3- Antispyware

a. Spyware is a malware installed in computer systems without user knowledge and intended to spy on users and their networks and relate information collected to whoever installed it may:

i. Monitor the user directly and send information collected.ii. Allow an outside party to control the computer (hacker creates a zombie)

b. Antispyware is usually bundled with antivirus software will ultimately find and remove spyware from the computer system.

4- Internet fraud : It is the crime of deliberately deceiving persons over the Internet in order toa. Damage them or their reputationb. Illegally obtain property or services from them

5- Other malware agents: a. Phishing :

i. A phishing email usually attempts to trick the recipient into revealing private and confidential information (bank references, credit card number, etc…)

ii. Anti-phishing software usually are used to identify phishing risks in suspicious emails and websites

1. Work tightly with the browser.2. Some browsers like Google Chrome and IE-9 and most modern browsers

have limited built-in anti-phishing capabilities.b. Spam comprises great volume of unsolicited junk mail that makes up more than half of

email messages exchanged world widec.

d. virus hoax is an email that warns of a virus that doesn’t exist. The warning usually comes in the form of serious warning of imminent disaster if you don’t behave promptly and delete files or click links and visit websites.

e. Zombie computer is any computer in a network that works as a slave under the control of a hacker who ultimately will use it to satisfy his hacking needs.

f. Botnet : is a network of zombies working together to overwhelm networks with: i. Denial-of-service attacks (example: overwhelmed network traffic)

ii. Breaking security codesiii. Generating a lot of spam iv. Botnet may be the source of a great deal of malware generated by hackers and

distributed over the Internet thru most Internet services.

6- How to defend yourself? a. Never let untrusted people manipulate your system or your storage mediab. Never leave your system or storage media unattendedc. Never click links received in e-mails that you don’t expect or trust d. If you happen to click a link, you must verify that it is taking you to a decent website.

Some links hijack you to websites that may harm your information system. e. Beware of hoaxes they may inflict a lot of damage in your information system if you

believe them and follow their directions. f. Networks and computer systems must be protected by using Firewalls which are

hardware and/or software that examine all incoming data packets and filters out the ones that are potentially dangerous.

g. Beware of war driving and never use unprotected WI-FI. Keep in mind there are criminals with mobile computers driving thru neighborhoods aiming to fin unprotected networks and use them to execute their crimes.

h. Encrypted messages will make your information more secured. There are many encryption technologies available for you to use and make your business comfortable with exchanging secured business messages.

7- System back up a. Necessity of back-up policy

i. Threats outlined above necessitate that business be equipped with effective back-up policy that will be able to:

ii. Have healthy duplicate files and databases available upon need.iii. Back-up files must be stored at a different location away from the working files

and databases; possibly on the web.iv. Back-up files must be frequently updated and easily accessible whenever we need

them and wherever we need to use them.b. Back-up frequency :

i. Full back-up: Copies all important files with no exception. It is usually performed once a year.

ii. Differential back-up: Copies all files that were updated or newly created or installed since the last full, differential or incremental back-up. And may be performed every 3 or 6 months.

iii. Incremental back-up: Copies all files that were updated or newly created or installed since the last incremental back-up. It is performed frequently every week or month.

c. Redundant Array of Independent Disks (RAID) technology :i. RAID technology consists of grouping many disk drives and makes them work

together in an array that may be configured as one or more logical drives.ii. RAID controller divides data into small stripes that may range from 8 to 64

kilobytes, and transfers resulting stripes in parallel to multiple drives in the array that enables the technology to:

1. Have data transfer rate much higher than non-RAID drives2. Use RAID to enhance business productivity factors3. Obtain high level of responsiveness4. The level of responsiveness is extremely important in modern multiple

user environment 5. Multiple user environment is considered to be a common characteristic

of modern information systemiii. Using RAID as back-up technology consists of applying also another technology

known as mirroring technology (figure 8-1) which consists of duplicating files and databases as illustrated below so that if a database goes bad its duplicate will take over and the system continue to work normally:

Figure 8-1 (RAID: Mirroring technology)

C 1CB 1BA1A