Its a VIRUS or a Trojan. BUgs are when software malfunctions. You need a malware checker eg Spybot search and destroy (free) and anti virus eg AVG (Free). IT may NOT be you who is sending them. Spam companies steal people's addresses and also some Malware will pick an address at random from your address book. If you forward one to me I can take a look at the header which will identify the real sender.