PRETEXTING
Obtaining information by pretending to be someone else. Federal laws prohibit using a false identity to get someone’s bank, financial, or telephone records, but claiming to be a reporter or job recruiter to extract other kinds of information is generally legal.

DATA HAUNTS
Methods for collecting electronically available information about someone without leaving any trace. These include intercepting emails by using secretly installed keystroke-logging software, illegally obtaining phone and bank records, and monitoring corporate-jet trips  by identifying tail numbers.

FALSE FLAGGING
Pretending that your client is the target of your investigation in order to elicit candid comments from business partners and rivals. This can help reveal who is bad-mouthing your client.

DUMPSTER DIVING
Recovering trash and other discarded material from a target’s office or home. It’s pretty common and is legal under most circumstances, such as when garbage is at the curb.

HARD SHOULDER
Digging up negative information as leverage to persuade someone to do what you want. Giving the hard shoulder was originally coined by Israeli intelligence agents.