I didn't use any software. I was checking her work BB from time to time which for some reason she never setup a password for. For me the signs were:

1) Constant Texting on her personal cell phone. This one was password protected.

2) Not having sex with me, but constantly reading Cosmo magazine.

3) Was not responding in anyway to my improvements.

4) Was depressed around the house and took no interest in the family or doing anything with us or doing any household chores.

5) Spending long hours at work

6) Buying expensive lingerie and wearing it to work

I suspected that something was going on for over a year. Was very satisfying to finally find proof and confront her about her actions. Watching her fantasy world come crashing down helped to gain back some of my confidence and take back some control over a painful situation.