HackAlert is said to becapable of monitoring, detecting and blocking such attempts and notify the website owner so that precautions or counter-measures can be taken. HackAlert is delivered as a cloud-based service, so websites can easily initiate the scanning. The service can also scale with the subscriber needs. HackAlert also claims to be able to detect (quickly) that a website has been blacklisted by Google. Because HackAlert is based on behaviors instead of signatures, it should be able to detect a threat that has not yet been identified.
HackAlert is available as a free on-demand service from http://hackalert.armorize.com.