How do investigators uncover what criminals search for online? Are all input queries saved on the harddrive?

[Dude]

For example, even if I clear my internet history, will my hard drive still record this question? Theoretically, if I looked up porn, is that filed on my harddrive as well? Basically, is all internet activity stored on the computer harddrive? Is it possible to remove these logs? Just curious. Thanks.

 

[Declan Donohue]

ISPs keep records of internet history.. but will not disclose them as it's illegal unless it's for good reason.. and yes queries and history are but when you delete you history it will be erased

 

[Colanth]

Your IP address is a matter of record. Which IP address searched for what, when, is retrievable from the various search engines. (And deleted files are recoverable, if they're worth the considerable cost involved.)