I am getting a large number of spam messages which appear to have been sent from my own e-mail address. Antivirus consistently isolates them in the spam folder but have I caught something that is using my computer to send messages I am unaware of?
It's called "spoofing", which can't be prevented. Spoofing is the "forgery" of an address, to hide the identity of the sender, and is usually done by an Automatic Spamming system, that blindly and randomly, runs through addresses in sequence. The sender information shown in e-mails (the "From" field) can be spoofed easily. It's not actually coming from or thru your account. This technique is commonly used by Spammers to hide the origin of their e-mails and leads to problems such as misdirected bounces. One type that's called "Self Spamming" appears to be coming "from" and going "to" the same address. I think, your case also falls in this category. Click on this LINK to know more about email spoofing.
It's just a trick spammers use to get your attention so that you may open the email to view the contents out of curiosity. If you do so, it may download other viruses/trojans/worms as a part of it and then try to gain access to your computer. Your account isn't in danger of being hacked when this happens. All you can do is delete the emails. You can't mark them as spam because you'd be blocking yourself. You have to understand that it's just a trick to mislead you.
You can run LiveUpdate until no more updates are available and then run a full system scan to make sure that you are protected.
I am getting a large number of spam messages which appear to have been sent from my own e-mail address. Antivirus consistently isolates them in the spam folder but have I caught something that is using my computer to send messages I am unaware of?