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Computer Security Threats
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This page provides basic information on computer security threats. The
computer security threats covered here are:
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Viruses
A software virus is
a parasitic program written intentionally to alter the way your computer
operates without your permission or knowledge.
A virus attaches copies
of itself to other files such as program files or documents and is inactive
until you run an infected program or open an infected document. When activated,
a virus may damage or delete files, cause erratic system behaviour, display
messages or even erase your hard disk.
A virus may spread
through email and instant messenger attachments, through infected files
on floppy disks or CD-ROMs, or by exploiting a security flaw in Microsoft
Windows.
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Macro
Viruses
Macros are simple
programs that can be written to automate repetitive tasks in a document
or make calculations in a spreadsheet. Macros can be written in documents
created by Microsoft Word, in spreadsheets created by Microsoft Excel
and in many other kinds of documents.
Macro viruses are
malicious macro programs that are designed to replicate themselves from
file to file and can cause damage to the files on your computer. They
spread whenever you open an infected file.
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Trojan
Horses
Trojan horses are
programs that appear to serve some useful purpose or provide entertainment,
which encourages you to run them. But these programs also serve a covert
purpose, which may be to damage files, to place a virus on your computer
or to allow a hacker to gain access to your machine. More commonly these
days, you can be enticed into running a Trojan by clicking a link on a
viral web site or in an email.
Trojans that allow
a hacker to gain access to your machine, called Remote Access Trojans
(RATs), are particularly prevalent at the moment. Over 50% of all spam
(unsolicited email) is sent from home or work computers that have been
compromised by RATs.
A Trojan horse is
not a virus because it does not replicate and spread like a virus.
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Worms
Worms are programs
that replicate and spread, often opening a back door to allow hackers
to gain access to the computers that they infect.
Worms can spread over the Internet by expoiting security flaws in the software of computers that are connected to the Internet. Worms can also spread
by copying themselves from disk to disk or by email.
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Zombies
A Zombie is a dormant
program that lies inactive on a computer. It can be activated remotely
to aid a collective attack on another computer. Zombies don’t normally
damage the computer on which they reside but can damage other computers.
Zombies often arrive
as email attachments and when the attachment is opened they install themselves
secretly and then wait to be activated.
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Phishing
A Phishing attack is when you are are sent an email that asks you to
click on a link and re-enter your bank or credit card
details. These emails can pretend to be from banks, Internet service
providers, on-line stores and so on, and both the email and the web site
it links to appear genuine. When you enter your bank or credit card details
they are then used fraudulently.
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Internet
Based Attacks
While your computer
is connected to the Internet it can be subject to attack through your network communications. Some of the
most common attacks include:
- Bonk – An attack
on the Microsoft TCP/IP stack that can crash the attacked computer.
- RDS_Shell – A method
of exploiting the Remote Data Services component of the Microsoft Data
Access Components that lets a remote attacker run commands with system
privileges.
- WinNuke – An exploit
that can use NetBIOS to crash older Windows computers.
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Viral
Web Sites
Users can be enticed, often by email messages, to visit web sites that contain viruses or Trojans. These sites are known as viral web sites and are often made to look like well known web sites and can have similar web addresses to the sites they are imitating.
Users who visit these sites often inadvertently download and run a virus or Trojan and can then become infected or the subject of hacker attacks.
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Spyware,
Adware and Advertising Trojans
Spyware, Adware and
Advertising Trojans are often installed with other programs, usually
without your knowledge. They record your behaviour on the Internet,
display targeted ads to you and can even download other malicious
software on to your computer. They are often included within
programs that you can download free from the Internet or that are on
CDs given away free by magazines.
Spyware doesn’t usually
carry viruses but it can use your system resources and slow down your
Internet connection with the display of ads. If the Spyware contains
bugs (faults) it can make your computer unstable but the main concern
is your privacy. These programs record every step that you take on
the Internet and forward it to an Ad Management Centre which reviews
your searches and downloads to determine your shopping preferences.
The Ad Management Centre will build up a detailed profile of you,
without your knowledge, and can pass this on to third parties, again
without your knowledge. Some Spyware can download more serious threats
on to your computer, such as Trojan Horses.
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Virus
Hoaxes
Virus hoaxes are messages,
usually sent by email, that amount to little more than chain letters.
They pretend to alert you to the latest "undetectable" virus and
simply waste your time and Internet bandwidth. The best course of action
is to delete these hoaxes - they can cause genuine fear and alarm in
the disabled, elderly and other vulnerable groups.
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Unsecured Wireless Access Points
If a wireless access
point, e.g. an ADSL (Broadband) Router, hasn't been secured then anyone
with a wireless device (laptop, PDA, etc) will be able to connect to it
and thereby access the Internet and all the other computers on the wireless
network.
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Bluesnarfing
The act of stealing personal data, specifically calendar and contact information, from a Bluetooth enabled device.
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Social Engineering
Tricking computer users into revealing computer security or private
information, e.g. passwords, email addresses, etc, by exploiting the
natural tendency of a person to trust and/or by exploiting a person's
emotional response.
Example 1: Spammers send out an email about victims of child abuse and
provide a link to click in the email for further information or to help
the victims. When the link is clicked the spammers know the email address
is "live" and
add it to their live list which they then use to target their spam.
Example 2: A company computer user is tricked into revealing the network
password by someone on the telephone who is impersonating the voice of
an employee in authority and who has a story of distress.
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Microsoft Office Document Metadata
The average Microsoft Word, Excel, etc document includes hidden metadata with details of who created it, who has worked on it, when it has been amended and quite possibly the text of all those changes as well. Viewing a Word document in a text editor can reveal the metadata in plain text at the start and finish of the document.
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