Worm

It is a malicious code that is delivered via an executable attachment in an email or over a computer network. Worms are able to capitalize on a security failing in the target computer and replicates itself on the infected system. This code is able to spread itself to other computers by automatically sending itself to every email address on a recipient’s contact list or address book.

Worms do not necessarily harm a computer or network like a virus, though they will use bandwidth. Commonly, worms are used by spammers to create a backdoor on an infected computer, allowing the worm’s owner to create a “zombie computer.” Networks of these zombie computers– often called botnets– are able to send spam or junk email while cloaking the website’s address. This is highly effective for spammers as their worm continues to replicate.

Email users, and especially mailing list owners, should be wary of unexpected email. Spammers and other worm creators have capitalized or profited by  using many tricks — including the use of realistic subject lines — to trick users into running their malicious codes. Email from strange addresses that have files or programs attached or link to websites, can often times spread worms. Email users should take care to ensure that their messages come from trusted sources, and that messages — especially those with attachments — do not deviate from their expectations.