A prolific variant of the Gumblar Trojan has performed another vanishing act, disappearing suddenly from malware figures gathered by Kaspersky Lab.

ScanSafe researchers are seeing renewed activity regarding Gumblar, a multifunctional piece of malware that spreads by attacking PCs visiting hacked Web pages.

Webmasters who find an annoying error message on their sites may have caught a big break, thanks to a slip-up by the authors of the Gumblar botnet.

Security researchers are seeing a resurgence of Gumblar, the name for a piece of malicious code that is spread by compromising legitimate but insecure Web sites.

Up to 40,000 Web sites have been hacked to redirect unwitting victims to another Web site that tries to infect PCs with malicious software, according to security vendor Websense.