The “Police Virus” is a trojan or a ransomware that installs on the computer unknowingly, and on the computer power-on it blocks the computer with a rather realistic message, translated in the local language with legal items of the local country/state (country flag plus logo of the federal/metropolitan police), that announces you the computer has been blocked because you have accessed illegal content such as child pornography or zoophilia. After explaining the maximum penalties, bot financial and freedom depriving, it lets you know that paying 100 of the local currency within 72h the computer will be unlocked and it will only be considered a warning.
Only a few of the solutions described on the internet work, the cleanup of the registries never works, as the virus removes any track when it is not used. Also most of the Malware protections are frauds, making you pay, or filling your computer with unneeded data. The only one working and is easy to uninstall afterwards is malwarebytes.org .
You can install the free version, run a quick scan (or full if you want) and the trojan is removed.