The trojan, called Riler.F, is dropped on to the system through another recently reported trojan that exploits a PowerPoint zero-day flaw. Symantec originally warned of the PPDropper trojan last week.
According to Symantec, Riler.F allows a remote attacker to have unauthorized access to the compromised computer. The company gives the trojan a damage level of "medium" but a distribution level of "low."
Microsoft isn't expected to release a patch to fix the PPDropper vulnerability until Aug. 8.