What is a program that migrates through networks and operating systems, typically attaching themselves to different programs and databases?

The program you are describing is commonly known as a "worm."

Worms are a type of malicious software (malware) that replicate themselves in order to spread to other computers. They often exploit vulnerabilities in operating systems or software to gain access and migrate through networks. Unlike viruses, worms do not need to attach themselves to a host program; instead, they can exist as standalone entities and typically use a network to send copies of themselves from one computer to another. This facilitates their propagation across the internet and intranets.

Worms can carry payloads that can cause harm to systems, such as deleting files, stealing sensitive data, or creating backdoors for further exploitation. Notable examples of worms include the “ILOVEYOU” worm and the “Conficker” worm, both of which caused widespread damage and disruption upon their release.

To protect against such malicious programs, it is essential to use up-to-date antivirus software, regularly patch operating systems and applications, and educate users about safe online practices.