Ity.im scans all added urls for viruses and malware on a continual basis. Anytime a detection occurs the shortened url is automatically and immediately removed.

Open source ClamAV beats McAfee and Norton
"In an informal test using variations of the EICAR test pattern plus 25-odd “in the wild” and community-submitted malware, Kaspersky scored the highest overall detection rate, with ClamAV second and Symantec Norton AV third. McAfee scored sixth."

Anti-virals get beat up at Untangle Fight Club
"Some well known virus signatures were run against the programs to test their engines. Some, like open source ClamAV (above), found them all. Others, like Watchguard, missed nearly all of them."