Is there any hackers who block your computer and ask you to pay money to unblock it?

Answer 1

That depends on what you mean by "block". If you mean block access to the internet - that's pretty tough to sustain since you can usually resolve the problem by calling your ISP to get them to fix the problem there or by restoring the portions of your operating system that take care of establishing connections to the network and running your browser or other applications that utilize the network.

On the other hand, there are some @sshole criminals who will cause the contents of your files to become encrypted and then demand that you pay money to them to get the necessary cryptographic key to decrypt and restore your files. They usually target companies because they can extort more money from them but they have been known to attack individual users. Like any hostage situation, there is no guarantee that the victim will get the hostage (in this case data) back intact once they have paid the ransom. This is one of many reasons that good practice is to back up all critical files regularly and store them offline separate from the primary storage so that in the event of data loss, you can restore the lost files.

Note that most (albeit not all) of these criminals operate from countries where there are no laws or little enforcement of existing laws to prosecute cyber crimes so victims are usually left with only two choices:

1. try to recover their data another way (hopefully from backups)

or

2. pay the ransom and hope that they will really get their data back.

Involving the law may not do any good if the authorities in the country where the criminals reside are unable or unwilling to prosecute.

I suppose that a sufficiently wealthy and unethical company could hire someone to hack back to the criminals, locate them, and then send some goons to rough them up to get the data back, but that's a pretty shady way to approach it and still not a guarantee that the data would be recovered. Better to use appropriate measures to prevent the intrusion in the first place and have backups to permit recovery if the preventive measures fail.