There are several paranoid checkers available, including:

Paranoia is a mental health state where an individual perceives hostile intent from others without adequate evidence. While the phrase "paranoid checker" is not a standard clinical term, it likely refers to the "checker" role in paranoia research—clinical tools and assessments used to identify and measure paranoid ideation. Clinical Assessment Tools (The "Checkers")

The keyword here is redundancy . The paranoid checker doesn't check once; they check until the anxiety temporarily subsides—which is usually only seconds before the next wave of doubt hits.

: High-speed checking of accounts, API keys, or system settings.

Paranoid thoughts can be a symptom of various mental health conditions, including paranoid personality disorder, anxiety disorders, and schizophrenia. However, they can also occur in people without a diagnosed mental health condition, often as a response to stress, trauma, or significant life changes.

The internet removes friction. The easier checking becomes, the more you do it.

This is the classic OCD subtype. The person has an inflated sense of responsibility and a catastrophic prediction. They believe that if they fail to check correctly, someone will die or be harmed in a terrible accident. "If I don't make sure the iron is unplugged, the house will burn down and I will be a murderer."