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Using Caution with Email Attachments
While email attachments are a popular and convenient way to send
documents, they are also a common source of viruses. Use caution when
opening attachments, even if they appear to have been sent by someone
you know.
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Why can email attachments be dangerous?
Some of the characteristics that make email attachments convenient and
popular are also the ones that make them a common tool for attackers:
- Email is easily circulated - Forwarding email is so simple that
viruses can quickly infect many machines. Most viruses don't even
require users to forward the emailthey scan a users' computer
for email addresses and automatically send the infected message to
all of the addresses they find. Attackers take advantage of the
reality that most users will automatically trust and open any message
that comes from someone they know.
- Email programs try to address all users' needs - Almost any
type of file can be attached to an email message, so attackers have
more freedom with the types of viruses they can send.
- Email programs offer many "user-friendly" features - Some email
programs have the option to automatically download email attachments,
which immediately exposes your computer to any viruses within the
attachments.
What steps can you take to protect yourself and others in your
address book?
- Be wary of unsolicited attachments, even from people you
know - Just because an email message looks like it came from your
mom, grandma, or boss doesn't mean that it did. Many viruses can
"spoof" the return address, making it look like the message came from
someone else. If you can, check with the person who supposedly sent
the message to make sure it's legitimate before opening any
attachments. This includes email messages that appear to be from your
ISP or software vendor and claim to include patches or anti-virus
software. ISPs and software vendors do not send patches or software in
email.
- Save and scan any attachments before opening them - If
you have to open an attachment before you can verify the source, take
the following steps:
- Be sure the signatures in your anti-virus software are up to date
(see Understanding
Anti-Virus Software for more information)
- Save the file to your computer or a disk
- Manually scan the file using your anti-virus software
- Open the file
- Turn off the option to automatically download attachments -
To simplify the process of reading email, many email programs offer
the feature to automatically download attachments. Check your settings
to see if your software offers the option, and make sure to disable
it.
- Consider additional security practices - You may be able
to filter certain types of attachments through your email software
(see Reducing
Spam) or a firewall (see Understanding
Firewalls).
Both the National Cyber Security Alliance and US-CERT have identified
this topic as one of the top tips for home users.
Authors: Mindi McDowell, Allen Householder
Copyright 2004 Carnegie Mellon University. Terms of use
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Last
updated
May 18, 2007
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