When I put my desktop computer into Standby, it comes out of standby all by itself just minutes later. I've also seen it come out of hibernation all by itself, but I've only tried that a couple times. Any idea why it's doing this? There isn't much going on in the background that I know of.
Might be similar to my problem Desktop reboots itself on sleep or hibernate
you should identify your operating system and motherboard model as well.
I was wondering why this was happening on my netbook with Windows 7. It's a very clean install, so I know malware wasn't an issue, and I've seen Windows 7 be very reliable with regards to sleep in the past, so I had a hard time accepting that.
Turns out in my BIOS I have it set to wake on keyboard/mouse activity. At the time, I had a USB mouse plugged in, and moving that even a little bit waked the laptop.
Just something to look for if you have the same issue -- there might be no need to be paranoid.