Ransomware is getting more complex, and anti-virus companies are worried they may not be able to decrypt ransomed files, according to a new report.

Malware Evolution: April to June 2006, Hidden Wars by anti-virus companyKaspersky Labs warns that ransomware authors are creating moresophisticated encryption algorithms in a bid to outfox securitycompanies, blackmail users and companies.

"We were able to decrypt 330- and 660-bit keys within a reasonably shortspace of time, but a new variant, with a longer key, could appear at anytime," said Aleks Gostev, a senior virus analyst at Kaspersky Lab. "IfRSA, or any other similar algorithm that uses a public key, were to beused in a new virus, anti-virus companies might find themselvespowerless, even if maximum computing power was applied to decrypting thekey."