That's the windows virus program. Could be a false positive which would require you setting up an exception. Some people run this stuff in a sandbox type setup so if they have viruses, they can catch it and just rebuild the system again. However, did anyone think to run it thru VirusTotal? Last time I ran litecoin core through it, it was one of the few coins that was completely clean. A lot will have stuff like "bitcoin miner" stuff flagged.