A number of American security professionals must have quickly switched from lazy Thanksgiving mode to high alert on Monday after receiving a flash warning from the FBI. A five-page document was sent out to US businesses' IT teams warning them against a highly destructive malware, which a group of hackers recently used to infiltrate several companies' computers, reports Reuters. In order for the companies to take preventative measures, the report contained the lowdown on the malware's technical details, such as its ability to override hard drives. The malicious code can apparently shut down and permanently disable computers, as well, making it impossible to retrieve files later on. The FBI issues "flash" warnings to businesses in order to update them about high-risk cyber threats. For this particular one, none of the malware's victims were named, and the agency also wouldn't confirm or deny when Reuters asked if Sony was one of them.