The tool, called Debank, was built by Finnish penetration testing company Fitsec, which has used the tool to scan its customers' machines, said company founder Toni Koivunen.
The tool works by scanning a computer's process memory, Koivunen said. Most malicious software these days is "packed," or compressed, before it is distributed. That can fool antivirus programs, since the malware can appear to be a different program each time it is repacked.
Koivunen said antivirus programs often use heuristics as an alternative way to detect malware aside from traditional signatures, but that method is not always as successful as a full memory sweep.
Debank looks at the program after it has been executed on a computer. Malware authors rarely change the core code of the program, which is what Debank analyzes.
Koivunen said Debank can detect nearly all variants of SpyEye, Zeus, CarBerp, Gozi and Patcher, five well-known banking malware programs. The malware has to be running for Debank to detect it and the tool only works on computers running Windows, he said.
Debank was able to detect more than 200 variants of Patcher after FitSec found a part of its code common to all variants. FitSec has also tested it against hundreds of variants of SpyEye, a particularly advanced piece of code that operates as part of a botnet. It can harvest credentials for online accounts and also initiate transactions even while a person is logged into their account.
Fitsec decided to just give the tool away and has made it available for download on their blog. "We had no reason to start charging for it," Koivunen said. "Basically, we hate malware."