We are seeing a lot of SpamTools now. These programs are installed on victim machines secretly, where they proceed to harvest email addresses. The harvested addresses are sent to the SpamTool’s master and used for mass mailings. In most cases, such spammer utilties are then de-installed automatically.
In the beginning, SpamTools harvested all email addresses on the infected machine. Today, we are seeing more and more SpamTools, which are picking and choosing: they fignore addresses containg substrings that point to antivirus and antispam vendors.
The result? When antivirus and anti-spam vendors do not receive mass mailings directly, it takes longer for the security community to react. Spammers get an additional window of opportunity to reach more people.
By the way, many virus writers have used this tactic when writing email worms, which also often do not send infected emails to antivirus vendors in an attempt to stay undetected just a bit longer.