Malware from China called the Warp Trojan infects a Windows computer and it then pretends to be a router and tells the real local subnet router to send traffic from other networked computers to the infected machine, so the malware can then try to compromise them through a man-in-the-middle attack.
“It has a direct impact on all the computers on the subnet because it will intercept traffic and make changes to the traffic,” said John Morris, principal security researcher at Kindsight Security Labs. The firm believes Warp Trojan hails from China and may be adware to drive traffic to websites there.
In some respects, Warp Trojan is an average malware in that it infects vulnerable Windows-based computers through known Adobe and Java exploits. What differentiates this malware is how the Trojan attempts to spread. It uses a man-in-the-middle attack that involves sending an unsolicited ARP request to the local subnet router in order to fool it into directing traffic to the infected machine.
“It uses ARP, the Address Resolution Protocol, and it’s telling the genuine router on the network that it, the Trojanized computer, is all the other computers on the network,” Morris said. As to whether it’s easy to trick routers into taking these fraudulent ARP requests, Morris said the testing done at the lab suggests that “a lot of routers don’t reject an unsolicited ARP.” Warp Trojan uses an older hacking tool called ZXarps to help carry out this part of the attack.
The result is when end users on a Windows computer network start to launch their browsers to request websites, they’ll go there, but they’ll get an extra iFrame HTML tag that will drive them to an infected website behind the scenes, according to Kindsight. These websites in China will attempt to push the Warp Trojan onto the computer, and if it’s vulnerable, the Trojan will infect it and the cycle will begin again.
Warp Trojan could potentially drop additional malware onto infected computers, Morris said. Its man-in-the-middle attack is something that makes it interesting because it raises the question of whether other fraudsters could use this approach for yet more evil purposes. “It’s inserting itself almost like a mock router into the network,” Morris said.