Computer

Maintenance

Security and Backups

System Maintenance

The basic routine maintenance tasks are:

Data backup

Malware management

File system maintenance

Backup

To backup is to create a redundant copy, so that

if anything should happen to the original file,

you have recourse to the backup.

The process can be as simple as copying files to

removable data device such as a CD/DVD or

Blu Ray Disc.

This can become a problem where files are too

big for this media or there are too many files, or

where too many discs are required.

A better solution is to use a backup utility to

create a single compressed file from a collection

of data files, and to split this over as many discs

as required.

This uses fewer discs and allows large files to be

backed up even if the file is larger than a disc

can hold.

Backup Types

Full system file backup; the entire PC is backed

up and restored as a unit.

Full mirror backup; as above, except a disk

image is used; any imperfections in the file

system will be reproduced on restore.

Data backup; only user data is backed up, the

system and applications have to be re-installed

from the original media.

Incremental backup; only data changed since last

full backup is saved.

Narrow-focus or State backup; aiming at

countering particular risks.

Risk levels and backup layering

Typically you will have a trade-off between

these factors:

Degree of protection; what risks are covered?

Ease of use; how often are backups done, how

"up to date" is the last one?

Volume of data to be backed up vs. capacity of

backup media

Your risks and levels of protection are:

Loss of a file; redundant copy on the same drive

Corruption of disk volume; backup on a

different disk volume

Failure of hard drive or computer system;

backup to another PC via LAN

Failure of multiple PCs (power spikes, site theft);

backup to off-system media

Site disaster (fire, floods); secure off-site storage

of off-system backup media

Ease of use levels are:

One-click backup of data to elsewhere on the

local hard drive; a reflex twitch

One-click backup to another hard drive on

LAN; as easy, but hits LAN bandwidth

One-click backup to single off-system storage

media; requires insertion of media

One-click backup to multiple off-system media;

requires waiting to change media

Formal locate-and-select backup procedures

What is malware?

Malicious wares are files, code or content that

act in an unexpected or undesirable manner;

includes trojans, viruses and worms - and yes,

some commercial software.

What is a virus?

A virus is code that causes itself to be

reproduced, infecting other disks or files and so

causing it to spread. Because Word auto-runs

macros, it is possible to write viruses that infect

Word documents.

Active content in HTML e-mail can also lead to

viruses.

Viruses may attempt to do no harm, but cause

problems as a side effect of bad coding or

compatibility issues.

What is a worm?

A worm is code that causes itself to spread over

a network, infecting other systems. Typically it

will do so by mailing itself to other addresses or

by attaching itself to all messages you send.

Because it automates the send to addresses

derived from your address book or mail, it is not

enough to know the sender of a message to trust

it.

Please Note

The distinction between worm (e.g. Happy99)

and virus (e.g. CAP) is blurred by malware such

as Zipped_Files and Melissa.

These arrive as trojans or viruses, may spread as

viruses, but also send themselves off directly as

worms do.

What is a trojan?

A trojan is a program or file that appears to be

desirable, useful or interesting, but harbors

malicious code.

"Joke" programs sent as e-mail, pirate software

downloaded from "warez" sites, and even web

pages and HTML e-mail "text" can be trojans.

Unlike worms and viruses, a pure trojan does

not have to infect other networks, systems, disks

or files to spread. However, many automate

their spread as worms.

What is a RAT? A Remote Access Trojan is a program that

effectively acts as a "virtual keyboard" on the

system, allowing hackers to access your

computer over the Internet. Files can be

downloaded and read, uploaded to your system,

or deleted and arbitrary programs can be run on

the system as well. As there is a live human at

the other end, with a high degree of access to

the PC, the behavior of a RAT is unbounded by

the code itself. In particular, passwords and

credit card numbers may be stolen and used.

What are attachments?

Arbitrary files can be sent along with e-mail

messages as enclosures or attachments.

Such files can be anything; trojans, trojan web

pages, virus infected documents and other files.

This is the most common form of malware

spread, and clueless users are not only falling

victim to this but are causing the problem by

allowing their systems to spread this to other

users.

What is active content?

Active content includes Java, JavaScript and

VBScript. These are programming or scripting

languages that are sent from a website to the

computer that visits the site, and run on that

computer, without the user's knowledge or

consent.

Because active content can go anywhere HTML

can go, and because many e-mail programs send

mail in HTML form, even the e-mail message

itself can be dangerous.

What is a payload? The payload is what the malware does that is

offensive! Includes:

1. Privacy; passwords, credit card numbers etc. sent

over Internet

2. Impersonation; sending messages as if from

yourself

3. Damage; deleting and trashing your data and

system files

4. Hardware damage; reprogramming the BIOS so

system cannot boot

5. Denial of service; interferes with system

functionality

Malware management

Simply running an antivirus utility is not enough,

even if it is kept up to date!

Some Windows-based antivirus utilities may

automate this process to some extent, by

accessing the Internet directly from within the

program. You should check for updates at least

once a week, and make sure your antivirus data

files do not become more than a month out of

date.

File system maintenance

Much can be done during system setup to

improve the survivability, maintainability and

recoverability of the file system and its data.

Thereafter, there are three tasks required on a

regular basis:

1. Check that sufficient free space is available;

ideally 50M+ on C: volume

Deleting unused software

Uninstalling unused software

Deleting data files

temporary internet files

2. Check the file system for errors, and manage

these

OS updates

Application software updates

Virus definitions

3. Defragment the file system once it is known to

be error-free