Worm:W32/Palevo.gen!A is a Generic Detection for variants from the Worm:W32/AutoRun malware family.
AutoRun worms spread by copying themselves into the root directories of hard drives and other writable media, such as USB memory sticks.
For more information, please see Worm:W32/Autorun.
About Generic Detections
Unlike more traditional detections (also known as signatures or single-file detections) a Generic Detection does not identify a unique or individual malicious program. Instead, a Generic Detection looks for broadly applicable code or behavior characteristics that indicate a file as potentially malicious, so that a single Generic Detection can efficiently identify dozens, or even hundreds of malware.
For more information, see the Generic Detection description.