Technology has gotten smarter and affairs have gone high-tech. Signs like a new password on a mobile phone or computer, or a change in the password at your bank or mobile service provider still count. But now, cheaters can fly under the radar by using technology to do their communication dirty work. Apps like SnapChat allow text messages, online chat sessions and pictures to last for a certain amount of time—and then disappear. Gliph sends completely cloaked, anonymous email. Lovers often sign up for a single Gmail account and trade messages in the "Drafts" folder so that nothing is sent. And the iPhone's Messages app is completely untraceable, bypassing mobile company's records, and never showing up on a phone bill. 

While these 10 signs aren't foolproof, a few taken in combination are indicators that something is amiss. My advice: Don't make accusations that you can't back up. If you suspect it, sit him down for a long talk about your concerns. If that nagging feeling doesn't disappear, you have some choices to make — and perhaps some investigations to start.