What is the purpose of signature files used to secure mobile devices and operating systems?

What is the purpose of signature files used to secure mobile devices and operating systems?

• They contain a record of historical and pending firmware and software updates.
• They contain a list of all user passwords.
• They contain a log of digital certificates and encryption keys associated with the user.
• They contain sample code from known viruses and malware that is used by security software to identify malicious software.
  

  Explanation: Antivirus and antimalware software compare the contents of a disk with sample virus and malware code included in signature files. If a comparison is found, the user can be notified and the virus can be isolated or removed.