Security researchers at the University of Calgary have identified a new malware they call "Typhoid." Typhoid impersonates the wireless router on your local network, effecting a man-in-the-middle attack that allows it to insert ads into the browsing sessions of all the other, uninfected users on the LAN.
Typically, adware authors install their software on as many machines as possible. But Typhoid adware comes from another person's computer and convinces other laptops to communicate with it and not the legitimate access point. Then the Typhoid adware automatically inserts advertisements in videos and web pages on the other computers. Meanwhile, the carrier sips her latté in peace — she sees no advertisements and doesn't know she is infected ¬- just like symptomless Typhoid Mary.