A blog post by Proofpoint researcher Kafeine noted that EITest had been used to deliver ransomware, information stealers and other malware since 2011.
Back in January last year, EITest had started to use social engineering schemes to entrap users and it was traced via server side artefacts to infections that had occurred as far back as 2011 when it was redirecting to a private exploit kit known as Glazunov.
From the beginning of 2014, EITest began directing users to the angler exploit kit.
Kafeine said that over the last month, EITest had been used in social engineering and tech support scams which led to Windows ransomware.
The sinkholing of EITest was achieved on 15 March after seizing the command and control domains. "Once seized, we pointed that domain to a new IP address to generate four new EITest C&C domains. These, in turn, were pointed to an abuse.ch sinkhole," Kafeine wrote.
"As a result of generating those new domains, we were able to substitute the malicious server with a sinkhole. We are now receiving the traffic from the backdoors on the compromised websites, freeing them from the EITest C&Cs and their visitors from the resulting malicious traffic and injects."
Analysing traffic from 15 March to 4 April, Kafeine noted that the sinkhole had received 44 million requests from 52,000 servers.
Despite having sinkholed and effectively put EITest out of business, Kafeine said EITest activity would continue to be monitored to see whether the attackers behind it would try to regain control of some of the compromised websites which had been involved in the infection chain.