Viruses Sent With My Address?

It has become quite common to receive notifications that you sent someone a virus or spam. Usually this is nothing to worry about.

In the “good old days”, when a computer infected with a mass-mailer virus sent itself to others, it used the email account of the current user and therefore all the infected emails used the sender's reply address. It was therefore easy to see from whence they came.

However, modern mass-mailer viruses can construct email messages without the need to rely on the host system's email program. To obfuscate their origin, they typically use a random reply address — either a nonsensical address or simply an address plucked from the host system's address book or mail store.

Thus if you receive delivery failures, read receipts or “infection” notifications for messages you do not recognise, the likelihood is that they did not originate from your system. Most likely they have come from somewhere else entirely and the virus has randomly selected your email address as the reply address, and therefore all the notifications for the infected messages will be sent to you.

There's not much you can do about somebody else's system generating infected emails in your name, and generally it can be difficult to trace where they really came from. The only clue you can assume is that they came from someone with your email address in their address book or in a message (so it is probably someone you know), and you can sometimes determine the originating ISP by looking at the properties of the message.

The only way to react to such messages is:

• Don't panic. Most likely the infected emails did not come from your system.

• Delete the message. There's not a lot of point keeping them, unless you are receiving a large volume — in which case it may be necessary to conduct an investigation with your ISP and they will want to see all the error notifications you are receiving.

• If someone you know calls you to complain about the virus you sent them, explain that it did not come from your system as viruses have a habit of using fake reply addresses.

• Maintain an antivirus system and ensure it is kept up to date.