computer science

Many of the most prolifi c viruses distribute themselves automatically by email.

Typically, email-aware viruses depend on the user double-clicking on an attachment.
This runs the malicious code, which will then mail itself to other people from that
computer. The Netsky virus, for example, searches the computer for fi les that may
contain email addresses, and then uses the email client on your computer to send
itself to those addresses. Some viruses, like Sobig-F, don’t even need to use your email
client; they include their own “SMTP engine” for constructing and sending the email
messages.

Any attachment that you receive by email could carry a virus; and launching such an
attachment can infect your computer.
Even an attachment that appears to be a safe type of fi le, e.g. a fi le with a .txt
extension, can pose a threat. That fi le may be a malicious VBS script with the real fi le
type (.vbs) hidden from view.

Some viruses, such as Kakworm and Bubbleboy, can infect users as soon as they read
email, exploiting a vulnerability in the operating system or mail program. They look
like any other message but contain a hidden script that runs as soon as you open the
email, or even look at it in the preview pane (as long as you are using Outlook with the
right version of Internet Explorer). This script can change system settings and send the
virus to other users via email.

Email viruses may compromise your computer’s security or steal data, but their most
common effect is to create excessive email traffi c and crash servers.
To avoid email viruses, you should run anti-virus software and avoid clicking on
unexpected attachments. You should also install the patches issued by software
vendors, as these can close down the vulnerabilities exploited by email viruses.