Viruses infect computers many different ways. Some of the most common methods are via file transfer and email. In and of itself, encryption does not prevent the transmission of malicious code of any kind. However, the use of encryption as a validation mechanism can provide a higher level of trust when receiving files and information from other people by ensuring that the source and contents of the message are trusted.
Digital signatures and message fingerprints can provide reasonable assurance that the file originates from the expected party and that it has not been tampered with. Encryption does not necessarily solve the problem completely though - a trusted source may unsuspectingly send an already infected file that is then validated.
Denial of Service Attacks Encryption can protect a user's credentials from capture, but is somewhat helpless against attacks that are intended to compromise a system. System compromise results from attacks against an operating system feature or service, and can only be rectified by secure development practices and analysis of the software. Encryption does not protect against network attacks such as denial of service, port scanning and other information gathering tactics. These attacks are generally independent of the use of encryption within a network or system.
