The volunteer-driven site, which is run by the husband and wife team of Paul and Robin Laudanski, had been coping with on-and-off attacks since February 13 but an intense wave that began around 3:45 PM EST today completely crippled the server capacity.
At 10:15 PM, despite industry-wide efforts at mitigation, CastleCops.com was still displaying a "Site Temporarily Unavailable" message.
"They got whacked real hard today. It was so strong that it knocked their ISP over," said a source involved in the scramble to mitigate the attack.
Law enforcement authorities are involved in the ongoing investigations.
CastleCops.com just celebrated its fifth anniversary as a high-profile anti-malware community. In partnership with Sunbelt Software, CastleCops.com runs the Phishing Incident Reporting and Termination (PIRT) Squad.