A variant of the Remote Control System (RCS) malware developed by an Italian company called Hacking Team is masquerading as a bookmark management application called Linkman, according to the main developer of a new malware scanning tool.The Detekt tool, launched last week to help users scan their computers for commercial spyware used by governments, has already led to the discovery of previously unknown malware variants, according to security researcher Claudio Guarnieri, who led development for the security app.RCS is sold to law enforcement and other government agencies around the world as a tool for legitimate computer surveillance. Hacking Team claims that it screens its customers, but independent reports suggest that the tool has been used in countries where human rights are poorly protected.It's not clear how the new RCS sample was distributed to users, but it used the Linkman icon and product name, Guarnieri said on Twitter.Outertech, the German software firm that develops the real Linkman program, pointed out that the RCS sample was signed with a digital certificate issued to an entity called Jagdeependra, while its legitimate application is signed with a certificate issued to Outertech."Please make sure the publisher is Outertech when installing Linkman," the company said on Twitter. "It's best you download Outertech products directly from http:\/\/outertech.com to make sure you get clean files."The new RCS sample was uploaded to the online scanning website VirusTotal, where as of Monday only two of the 54 supported antivirus engines detected it as malicious.Antivirus company Bitdefender found three files in its database signed with the Jagdeependra digital certificate, which has since been revoked by the issuing certificate authority -- Comodo.One of those files is different than the one announced by Guarnieri, but also uses the Linkman product name and icon. The sample has been in Bitdefender's database since Oct. 14, suggesting that the effort to pass off RCS as Outertech Linkman is over a month old.The third sample is even more interesting, because it masquerades as Realtek NIC Diagnostic Utility, a program developed by chipset manufacturer Realtek Semiconductor.It's not clear at the moment if the fake Realtek NIC Diagnostic Utility is also a variant of RCS or some other malware signed by attackers with the same digital certificate, said Bogdan Botezatu, a senior e-threat analyst at Bitdefender.This sample is also available on VirusTotal, where it was first submitted on Oct. 13.