chapter 8. copyright pearson prentice-hall 2010 some attacks inevitably get through network...

Chapter 8

Copyright Pearson Prentice-Hall 2010

Some attacks inevitably get through network protections and reach individual hosts

In Chapter 7, we looked at operating system and data hardening

In Chapter 8, we look at application hardening

This is the last chapter on protection.◦ Chapter 9 focuses on response

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Executing Commands with the Privileges of a Compromised Application

◦ If an attacker takes over an application, the attacker can execute commands with the privileges of that application

◦ Many applications run with super user (root) privileges

◦ In Today’s News…

CarrierIQ

Hidden surveillance software, is embedded into most mobile devices, including Android, Nokia, Blackberry

With you guessed it Root Access!

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One of the most important findings in cybersecurity over the past several years has been the understanding most often asserted by White House officials that "offense must inform defense." Only people who understand how attacks are carried out can be expected to be effective defenders.


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Copyright Pearson Prentice-Hall 2010 5

Copyright Pearson Prentice-Hall 2009 6

But if we don’t understand these vulnerabilities

We Can’t ask the correct questions

We Can’t deploy the proper controls

We Can’t test the controls are working

7Copyright Pearson Prentice-Hall 2009

mydebitcredit.com

Reviewing one of the disabled files, this is the malicious code that wasinjected at the beginning of the file:<?php /**/eval(base64_decode("aWYoZnVuY3Rpb25fZXhpc3RzKCdvYl9zdGFydCcpJiYhaXNzZXQo... (this continues on)

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Buffer Overflows

Stack Overflows

Cross-Site Scripting (XSS)

SQL-Injection


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Buffer Overflow Attacks

◦ Buffers are places where data is stored temporarily

◦ A condition at an interface under which more input can be placed into a buffer or data holding area than the capacity allocated, overwriting other information.

◦ Consequences include:

Corruption of data

Unexpected transfer of control (to an unauthorized program)

Memory access violations

Program termination

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ReturnAddressData Buffer

1.Write Return

Address

2.Add Datato Buffer

3. Direction of Data Writing 4.Overwrite

ReturnAddress

5.Start of

Attack Code

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Lets say this is computer memory running an application.The application is paused to get dataSo the address of where the application is before interruption is storedSo we can return after getting data, but the return address is overwritten and after the pause, a new program begins processing

ApplicationApplication

VariablesVariables

Return AddressReturn Address

ApplicationApplication

OverwritesReturn Address

VariablesVariables

New Return AddressNew Return Address

Exploit/ShellCodeExploit/ShellCode

Identify existence of a buffer overflow vulnerability

Application must require external data that the attacker can control

Understanding of how buffer will be stored in memory

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Inspect Code

Fuzzing (discussed later)

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Specifically written for:◦ A particular processor (e.g. Intel)

◦ A particular Operating System (Windows XP SP3)

◦ A particular Application

◦ Written in Machine code Requires High level of Expertise But Not anymore….

Metaspolit Project

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Compile-Time Defenses◦ Harden Program Code

Run-Time Defenses◦ Detect and Abort Buffer Overflow Attacks

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Choose High-Level Program Language◦ Higher level languages better address

Data Types (text in text, integer in integer) Better controls over data type manipulations Perform range checks

◦ Downside Cost Further away from underlying machine

language May not be able to access certain instructions

and hardware resources may be lost May not be possible to use these languages for

Device Drivers

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Safe Coding Techniques◦ Programmers need to inspect code for Security

◦ OpenBSD – Secure Unix Operating System

◦ Coding for Graceful Failure

◦ Any Code written to a buffer must FIRST check to ensure sufficient space is available

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Stack Protection◦ Program Entry and Exit code checks for evidence of

corruption

◦ If found program is aborted

◦ Example: Stackgaurd Uses a “Canary” value which is inserted in memory

right below the return address This value is known A check of this value at the known memory

location before using a return address can determine if overflow changes occurred

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Stack Protection◦ Stackshield and Return Address Defender (RAD)

◦ When new function is called, return address is copied to a safe area of memory

◦ When function is finished, the Return Address in stack is compared against address in safe memory

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Executable Address Space Protection◦ Do Not allow executable code (applications) to run

from the buffer

Address Space Randomization◦ Change location of buffer in memory randomly for

each process being run.

Guard Pages◦ Gaps are placed between memory locations, thus

overflow data goes into gaps and does not Overwrite data

◦ If data is written to one of these gaps, the program is aborted

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Few Operating Systems but Many Applications◦ Application hardening is more total work than

operating system hardening

Understanding the Server’s Role and Threat Environment◦ Just run minimum necessary applications on a

server

◦ If Email, just run email

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Basics◦ Physical Security◦ Backup◦ Harden the Operating System◦ Etc.

Minimize Applications◦ Main applications◦ Subsidiary applications

Wordpress Plugins (mydebitcredit.com)◦ Be guided by security baselines

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Create Secure Application Program Configurations◦ Use baselines to go beyond default installation

configurations for high-value targets

◦ Avoid blank passwords or well-known default passwords

Install Patches for All Applications

Minimize the Permissions of Applications◦ If an attack compromises an application with low

permissions, will not own the computer24


Add Application Layer Authentication, Authorizations, and Auditing◦ More specific to the needs of the application than

general operating system logins

◦ Can lead to different permissions for different users

Implement Cryptographic Systems◦ For communication with users

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Custom Applications◦ Written by a firm’s programmers

◦ Not likely to be well trained in secure coding

The Key Principle◦ Never trust user input

◦ Filter user input for inappropriate content

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Software Quality Testing◦ Use of Structured Design Process (SAD)

◦ Testing to eliminate as many bugs as possible Variations of likely data input to uncover bugs Focus is on triggering bugs and fixing flaw

Secure Coding◦ Attacker targets a known bug and exploits it

◦ Triggered by input much different than that tested for software quality, thus not likely caught during QA

◦ Increase Time and amount of Code needed Conflicts with Business pressures for SAD

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Input

Processing

Output

We’ll examine only Input…

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Most common points of failure

Input is:◦ Any data that originates from outside of the application

Keyboard Files Network connections Data from operating environment Configuration settings

◦ Data value is not known by the programmer when code is written (a variable)

◦ Data size and Data type have to be verified by code

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Data Interpretation◦ What data is being input

◦ What is the meaning of the data

Data Input can be:◦ Textual

◦ Binary 0s and 1s are interpreted as:

Integers, floating point numbers, character strings Must be validated

Meaning of Data◦ Is it a URL

◦ Email Address

◦ Integer

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Input data accidently or deliberately changes the operations of the program.

Happens often when input data are passed between functions of a program as parameters (variables)◦ Input to one program is Output to another

SQL injection◦ SQL query inserted as input or part of input

Code injection◦ Code that is executed by the system (e.g. buffer

overflow)

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Buffer Overflow Attacks◦ In some languages, specific actions are needed

◦ In other languages, not a major problem

Login Screen Bypass Attacks◦ Website user gets to a login screen

◦ Instead of logging in, enters a URL for a page that should only be accessible to authorized users

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Cross-Site Scripting (XSS) Attacks

◦ One user’s input can go to another user’s webpage

◦ Usually caused if a website sends back information sent to it without checking for data type, scripts, etc.

◦ Example, If you type your username, it may include something like, “Hello username” in the webpage it sends you

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Example◦ Attacker sends the intended victim an e-mail

message with a link to a legitimate site

◦ However, the link includes a script that is not visible in the browser window because it is beyond the end of the window

◦ The intended victim clicks on the link and is taken to the legitimate webpage

◦ The URL’s script is sent to the webserver with the HTTP GET command to retrieve the legitimate webpage

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Example◦ The webserver sends back a webpage including the script

◦ The script is invisible to the user (browsers do not display scripts)

◦ But the script executes

◦ The script may exploit a vulnerability in the browser or another part of the user’s software

Comment Example◦ Hey I really liked that blog post

◦ <script>document.location=‘http://hacker.web.site’</script>

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Input data should be inspected

Sounds easy, look for <script> as part of input and block…. But

HTML character entities◦ < = <

Input should be compared to what is wanted by the program◦ NOT against known dangerous values

◦ See Encoding above

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SQL Injection Attacks◦ For database access

◦ Programmer expects an input value—a text string, number, etc. May use it as part of an SQL query or

operation against the database Say to accept a last name as input and return

the person’s telephone number

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SQL Injection Attacks◦ Attacker enters an unexpected string

For example: a last name followed by a full SQL query string Bob’ drop table suppliers==

The program may execute both the telephone number lookup command and the extra SQL query

This may look up information that should not be available to the attacker

It may even delete an entire table38


Must Require Strong Secure Programming Training◦ General principles

◦ Programming-language-specific information

◦ Application-specific threats and countermeasures

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Importance of WWW Service and E-Commerce Security◦ Cost of disruptions, harm to reputation, and

market capitalization

◦ Customer fraud

◦ Exposure of sensitive private information

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Webservice versus E-Commerce Service

◦ WWW service provides basic user interactions

Microsoft Internet Information Server (IIS), Apache on UNIX, other webserver programs

◦ E-commerce servers add functionality: Order entry, shopping cart, payment, etc.

Links to internal corporate databases and external services (such as credit card checking)

Custom programs written for special purposes

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E-Commerce Software

SubsidiaryE-Commerce SoftwareWebserver

Software Component(PHP, etc.)

CustomPrograms


Website Defacement

Numerous IIS buffer overflow attacks◦ Many of which take over the computer

IIS directory traversal attacks

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root

WWW Root etcpasswd

ReportsQuarterly.html

Public

TechReportsmicroslo.doc

.. etc

Reports

URL:/Reports/Quarterly.html

URL:/../etc/passwd

Users should only be able to reach files below the WWW root, which is below the true system

root

Users should only be able to reach files below the WWW root, which is below the true system

root


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root

WWW Root etcpasswd

ReportsQuarterly.html

Public

TechReportsmicroslo.doc

.. etc

Reports

URL:/Reports/Quarterly.html

URL:/../etc/passwd

In URLs, .. meansmove up one level.If allowed, user can

get outside the WWW root box, into

other directories

In URLs, .. meansmove up one level.If allowed, user can

get outside the WWW root box, into

other directories


IIS directory traversal attacks (Figure 8-8)

◦ Companies filter out “..”

◦ Attackers respond with hexadecimal and UNICODE representations for “..” and “..”

Hex code for .. = 2E2E

Unicode for .. 002E002E

All three interpreted the same by webserver

◦ Typical of the constant “arms race” between attackers and defenders

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Patching the WWW and E-Commerce Software and Their Components◦ Patching the webserver software is not enough

◦ Also must patch e-commerce software

◦ E-commerce software might use third-party component software that must be patched

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Other Website Protections◦ Website vulnerability assessment tools, such as

Whisker

◦ Reading website error logs

◦ Placing a webserver-specific application proxy server in front of the webserver

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PCs Are Major Targets◦ Have interesting information and can be attacked

through the browser

Client-Side Scripting (Mobile Code)◦ Java applets: Small Java programs

Usually run in a “sandbox” that limits their access to most of the system

◦ Active-X from Microsoft; highly dangerous because it can do almost everything

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Client-Side Scripting (Mobile Code)◦ Scripting languages (not full programming

languages)

A script is a series of commands in a scripting language

JavaScript (not scripted form of Java)

VBScript (Visual Basic scripting from Microsoft)

A script usually is invisible to users

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Malicious Links

◦ User usually must click on them to execute (but not always)

◦ Tricking users to visit attacker websites

Social engineering to persuade the victim to click on a link

Choose domain names that are common misspellings of popular domain names

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You like beef?click here.You like beef?click here.

http://www.micosoft.comhttp://www.micosoft.com


Other Client-Side Attacks

◦ File reading: turn the computer into an unintended file server

◦ Executing a single command

The single command may open a command shell on the user’s computer

The attacker can now enter many commands

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C:>C:>


Other Client-Side Attacks◦ Automatic redirection to unwanted webpage

On compromised systems, the user may be automatically directed to a specific malicious website if they later make any typing error

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Other Client-Side Attacks◦ Cookies

Cookies are placed on user computer; can be retrieved by website

Can be used to track users at a website

Can contain private information

Accepting cookies is necessary to use many websites

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Enhancing Browser Security◦ Patches and updates

◦ Set strong security configuration options (Figure 8-12) for Microsoft Internet Explorer

◦ Set strong privacy configuration options (Figure 8-13) for Microsoft Internet Explorer

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Copyright Pearson Prentice-Hall 2010Copyright Pearson Prentice-Hall 200958


Content Filtering

◦ Malicious code in attachments and HTML bodies (scripts)

◦ Spam: Unsolicited commercial e-mail

◦ Volume is growing rapidly: Slowing PCs and annoying users (porno and fraud)

◦ Filtering for spam also rejects some legitimate messages

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Inappropriate Content◦ Companies often filter for sexually or racially

harassing messages

◦ Could be sued for not doing so

Extrusion Prevention for Intellectual Property (IP)

Stopping the Transmission of Sensitive Personally Identifiable Information (PII)

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Employee training

◦ E-mail is not private; company has right to read

◦ Your messages may be forwarded without permission

◦ Never put anything in a message the sender would not want to see in court, printed in the newspapers, or read by his or her boss

◦ Never forward messages without permission

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E-Mail Encryption (Figure 8-17)

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Benefits of Retention◦ Major part of corporate memory

◦ Often need to retrieve old mail for current purposes

Dangers of Retention◦ Legal discovery process

◦ Defendant must supply relevant e-mails

◦ Potentially very damaging information

◦ Always expensive

◦ Even if very expensive to retrieve, firms must pay whatever is necessary to do so

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Accidental Retention◦ Even if firms delete e-mail from mail servers,

◦ May be stored on backup tapes

◦ Users will often store copies on their own computers

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Legal Archiving Requirements◦ Many laws require retention

Securities and Exchange Commission Many labor laws Involuntary terminations Public information about job openings Medical problem complaints that may relate to

toxic chemicals

◦ Laws vary in duration of storage requirements

◦ Fines or summary judgments if fail to retain and produce required e-mails

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U.S. Federal Rules of Civil Procedure◦ Specify rules for all U.S. federal civil trials

◦ Specifically address electronically stored information

◦ Initial discovery meeting Defendant must be able to specify what

information is available Comes shortly after a civil lawsuit begins Unless carefully thought through before hand,

will fail

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U.S. Federal Rules of Civil Procedure◦ Holds on destruction

Must be put in place if it is foreseeable that a lawsuit will soon begin

Must have strong hold procedures to place holds on all electronically stored information

Archiving Policies and Processes◦ Must have them

◦ Must reflect a firm’s legal environment

◦ Must be drawn up with the firm’s legal department

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Message Authentication◦ Spoofed messages can frame employees or the

firm itself

◦ Need message authentication to prevent spoofed sender addresses

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Concept MeaningTransport The carriage of voice between the two

parties

Signaling Communication to manage the network.

Call setup

Call teardown

Accounting

Etc.


Eavesdropping

Denial-of-Service Attacks◦ Even small increases in latency and jitter can be

highly disruptive

Caller Impersonation◦ Useful in social engineering

◦ Attacker can appear to be the president based on a falsified source address

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Hacking and Malware Attacks◦ Compromised clients can send attacks

◦ Compromised servers can do disruptive signaling

Toll Fraud◦ Attacker uses corporate VoIP network to place

free calls

Spam over IP Telephony (SPIT)◦ Especially disruptive because it interrupts the

called party in real time

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Basic Corporate Security Must Be Strong

Authentication◦ SIP Identity (RFC 4474) provides strong

authentication assurance between second-level domains

Encryption for Confidentiality◦ Can add to latency

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Firewalls◦ Many short packets

◦ Firewall must prioritize VoIP traffic

◦ Must handle ports for signaling SIP uses Port 5060 H.323 uses Ports 1719 and 1720 Must create an exception for each

conversation, which is assigned a specific port Must close the transport port immediately

after conversation ends

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NAT Problems◦ NAT firewall must handle VoIP NAT traversal

◦ NAT adds a small amount of latency

Separation: Anticonvergence◦ The convergence goal for data and voice

◦ Virtual LANs (VLANs) Separate voice and data traffic on different

VLANs Separate VoIP servers from VoIP phones on

different VLANs

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Widely Used Public VoIP Service

Uses Proprietary Protocols and Code◦ Vulnerabilities? Backdoors? Etc.

◦ Firewalls have a difficult time even recognizing Skype traffic

Encryption for Confidentiality◦ Skype reportedly uses strong security

◦ However, Skype keep encryption keys, allowing it to do eavesdropping

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Inadequate Authentication◦ Uncontrolled user registration; can use someone

else’s name and so appear to be them

Peer-to-Peer (P2P) Service◦ Uses this architecture and its proprietary (and

rapidly changing) protocol to get through corporate firewalls

◦ Bad for corporate security control

Skype File Sharing◦ Does not work with antivirus programs

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Databases◦ Often used in mission-critical applications

◦ Relational databases: Tables with rows (entities) and columns (attributes)

◦ As discussed earlier, avoid SQL injection attacks

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Databases◦ Restrict Access to Data

Restrict users to certain columns (attributes) in each row For instance, deny access to salary column to most

users

Limit access control to rows For instance, only rows containing data about people in

the user’s own department

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Databases◦ Restrict Granularity

Prevent access to individual data

Allow trend analysts to deal only with sums and averages for aggregates such as departments

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Presence servers merely tell the clients that others exist and what their IP addresses are


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All transmissions go through relay servers when relay servers are used.


Spreadsheet Security

◦ Spreadsheets are widely used and the subject of many compliance regulations

◦ Need for security testing

◦ Spreadsheet vault server to implement controls (Figure 8-25)

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1.The vault server stores

spreadsheets and strongly controls access to them.AuthenticationAuthorizations

Auditing

1.The vault server stores

spreadsheets and strongly controls access to them.AuthenticationAuthorizations

Auditing

2.Spreadsheets record each

change for auditing purposes

2.Spreadsheets record each

change for auditing purposes


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3.Cryptographic Protections for Transmissions

3.Cryptographic Protections for Transmissions

4.Strong Client

Security

4.Strong Client

Security


TCP/IP Supervisory Protocols

◦ Many supervisory protocols in TCP/IP ARP, ICMP, DNS, DHCP, LDAP, RIP, OSPF, BGP,

SNMP, etc.

◦ The targets of many attacks

◦ The IETF has a program to improve security in all (the Danvers Doctrine)

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Example◦ Simple Network Management Protocol (SNMP)

◦ Messages

GET messages to get information from a managed object

SET messages to change the configuration of a managed object

SET is often turned off because it is dangerous

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Example◦ SNMP versions and security

Version 1: No security

Version 2: Weak authentication with a community string shared by the manager and managed devices

Version 3: Pair-shared secrets, optional confidentiality, message integrity, and anti-replay protection

Still needed: public key authentication

89


IT Security People Must Work with the Networking Staff◦ To ensure that appropriate security is being

applied to supervisory protocols

◦ Not a traditional area for IT security in most firms

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mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.

Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Publishing as Prentice HallPublishing as Prentice Hall

chapter 8. copyright pearson prentice-hall 2010 some attacks inevitably get through network...

Documents

data hardeningin chapter

external data

application hardeningthis

buffer overflow attacksbuffers

individual hostsin chapter

intela particular

particular processor

computer memory