Two security companies issued alerts about a troublesome new type of Trojan program known variously as Trojan 55808 and Stumbler. The program isn’t a worm and can’t spread itself or perform any malicious actions on hosts that it infects, said Dan Ingevaldson, engineering manager with X-Force at Internet Security Systems Inc. (ISS) in Atlanta, which issued an alert. Instead, the Trojan must be installed manually on victims’ computers running the Linux operating system. Once installed, the Trojan runs quietly in the background and acts as a “distributed port scanner,” randomly searching the Internet for machines with valid IP addresses and open ports, according to Intrusec Inc. in Roswell, Ga., which also issued an alert. Full Story