Use caution with email attachments

Why email attachments can 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.

Forwarding email is so simple that viruses can quickly infect many machines. Most viruses don't even require users to forward the email—they 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.

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.

Lastly, many email programs have the option to automatically download email attachments, which immediately exposes your computer to any viruses within the attachments.

Steps 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 type of email spoofing often happens during tax filing season "from" the IRS. If you are unsure about an attachment, employees should contact their IT Provider and students should contact the OIT HelpDesk.
  • Keep software up to date
    Install software patches so that attackers can't take advantage of known problems or vulnerabilities. Many operating systems offer automatic updates. If this option is available, you should enable it.
  • Trust your instincts
    If an email or email attachment seems suspicious, don't open it, even if your anti-virus software indicates that the message is clean. Attackers are constantly releasing new viruses, and the anti-virus software might not have the signature. Don't let your curiosity put your computer at risk.
  • 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:
    1. Be sure your anti-virus software is up to date.
    2. Save the file to your computer.
    3. Manually scan the file using your anti-virus software.
    4. If the file is clean and doesn't seem suspicious, go ahead and open it.
  • 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.
Again, if you are unsure about an attachment, employees should contact their IT Provider and students should contact the OIT HelpDesk.

Source: https://www.us-cert.gov/ncas/tips/ST04-010

Last Updated: August 23, 2016