How to protect
yourself against email-borne viruses
In recent weeks there have been several mass-mailing
viruses released on the Internet. It is important for
all Vasians to understand the risks posed by these pieces
of malicious code and the steps necessary to protect
their systems from virus infection.
I. Description
Over the past week, we have seen two more mass-mailing
viruses, W32/Bagle and W32/Novarg (also known as MyDoom),
impact a significant number of home users and sites.
The technology used in these viruses is not significantly
different from prior mass-mailing viruses such as W32/Sobig
and W32/Mimail. Unsolicited email messages containing
attachments are sent to unsuspecting recipients. They
may contain a return address, a provocative envelope,
or something else that encourages its receiver to open
it. This technique is called social engineering. Because
we are trusting and curious, social engineering is often
effective. The widespread impact of these latest viruses,
which rely on human intervention to spread, demonstrates
the effectiveness of social engineering.
It continues to be important to ensure that anti-virus
software is used and updated regularly, that attachments
are examined on mail servers, and that firewalls filter
unneeded ports and protocols. It also remains necessary
that users be educated about the dangers of opening attachments,
especially executable attachments.
II. Impact
A virus infection can have significant consequences
on your computer system. These consequences include,
but are not limited to:
Information disclosure |
Mass-mailing viruses typically harvest
email addresses from the address books or files
found on an infected system. Some viruses will
also attempt to send files from an infected host
to other potential victims or even back to the
virus author. These files may contain sensitive
information. |
Add/Modify/Delete files |
Once a system is compromised, a virus could
potentially add, modify or delete arbitrary files
on the system. These files may contain personal
information or be required for the proper operation
of the computer system. |
Affect system stability |
Viruses can consume significant amounts of computer
resources causing a system to run slowly or be
rendered unusable. |
Install a backdoor |
Many viruses will install a backdoor on an infected
system. This backdoor may be used by a remote attacker
to gain access to the system, or view/add/modify/delete
files on the system. These backdoors may also be
leveraged to download and control additional tools
for use in distributed denial-of-service (DDoS)
attacks against other sites. |
Attack other systems |
Systems infected by viruses are frequently used
to attack other systems. These attacks frequently
involve attempts to exploit vulnerabilities on
the remote systems or denial-of-service attacks
that utilize a high volume of network traffic. |
Send unsolicited bulk email (spam)
to other users |
There have been numerous reports of spammers
leveraging compromised systems to send unsolicited
bulk email. Frequently these compromised systems
are poorly protected end user computers (e.g.,
home and small business systems). |
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