At my job everyone gets a background check before they start. I assume it includes at least a basic web search for their name, which could potentially turn up social media but to my knowledge its primarily focused on turning up legal issues. If the job involves handling money I believe its more thorough than the standard background check but I don’t know the specifics. You only get drug tested if your job requires operating heavy machinery or employer owned vehicles, or if you’re involved in an accident where employer insurance gets involved you can be required to do a drug test after the accident.