Computer intruders read newspapers and company press releases, and visit Internet sites, to find job listings. Often, companies disclose too much information about the types of hardware and software used to attract prospective employees. Once the intruder has knowledge of the target's information systems, he is armed for the next phase of attack. For example, by knowing that a particular company uses the VMS operating system, the attacker may place pretext calls to determine the release version, and then send a phony emergency security patch made to appear as if it came from the software developer. Once the patch is installed, the attacker is in.