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