Why are some attachments dangerous?

Some email attachment types can be exploited to spread malware in the form of a virus, worm or trojan. Sometimes this is done like the ILOVEYOU virus which relied on the recipients launching the attachment (by double-clicking it).

If you receive a program (file type ".exe") by email and launch it, then you are allowing that program full control of your PC. It can do anything that you can, including deleting all of your files and then emailing itself to your friends. Even if the sender is a colleague you cannot know if they sent the email or if it was sent by a virus controlling their PC. For this reason the transmission of executable programs by email is regarded as bad practice.

Even though our anti-virus software protects us, new malware appears frequently and there is always a window of danger until the anti-virus is updated. Therefore we have decided that our email systems should block the reception and transmission of the more dangerous attachment types.

How does it work?

The mail gateways will discard any email containing the proscribed attachment types and will send a notification to the sender ("from" address).

But I need to send an executable!

You can rename it (eg. "program.exe" --> "program.exe-remove-this") or you can compress it into a ".zip" using WinZip. In that form, it will usually not be blocked.

Are ". zip" safe?

Recently viruses have appeared that arrive in e-mail as a ".zip" attachment. Some exploit a flaw in the unzipping software. Some are viruses packed into an encrypted (password protected) ".zip" archive and rely on the recipient unzipping them (double clicking and entering the password that is in the accompanying e-mail text).

Temporary attachment blocking

It may occasionally be necessary to block, temporarily, ".zip" or any other file attachment types during a new virus outbreak until other corrective action(s) can be completed.

List of attachment types that are blocked: