It might detect activity only once a volcano has started erupting.

And pointed questions are being asked about a department that could not detect potentially illegal activity until well after the fact.

Check your credit report at least once a year to correct errors and detect unauthorized activity.

Human spotting remains an important part of detecting activity, but increasingly electronic systems are used.

We've improved our ability to detect and stop terrorist activity.

"Computer, do you detect any evidence of current or former biological activity in these samples?"

That can make it hard to detect illegal activity.

The sensors pads detect electrical activity on the surface of the brain.

The agency insists that its monitoring can detect nuclear activity.

The following sections describe different ways to detect suspicious activity.