Russian authorities have not confirmed the details, but IT security firms have reported a decline in the use of both kits designed to enable criminals to exploit security vulnerabilities, according to the BBC.
Sources in the security industry also claim that the daily updates of the kits have come to a halt.
First released in 2010, the Blackhole kit is among the most popular exploit kits available to cyber criminals, costing just $1,500 a year or $200 a week and providing online support.
The web-based application has typically incorporated the latest exploits, including several zero-day or near zero-day exploits.
More on Blackhole
The kit enables criminals to exploit a range of vulnerabilities in Java, Adobe’s Flash media player, Adobe Reader and Microsoft Windows software to install malware designed to extort money, steal financial records, record keystrokes and hijack PCs for use in botnets.
Independent security analyst Graham Cluley said if it turns out to be true that the creator of Blackhole and Cool is under arrest, it is a “real coup” for cyber crime-fighting authorities.
“Hopefully [the arrest] will cause disruption to the development of one of the most notorious exploit kits the web has ever seen,” he wrote in a blog post.
However, Cluley said it was worth remembering that nature abhors a vacuum, and there would surely be other online criminals waiting to take the place of Blackhole and Cool.