Which of the following are valid phases of a computer virus ?

1. Dormant Phase The virus is hidden and inactive on the system — waiting. It does no damage at this stage and is difficult to detect.

2. Propagation Phase The virus copies and spreads itself to other files, programs, or systems — replicating to infect as many targets as possible.

3. Triggering Phase The virus is activated by a specific event — such as a date, number of times a file is opened, or a user action. This "trigger" wakes the virus up.

4. Executing Phase The virus carries out its intended damage — deleting files, corrupting data, displaying messages, or crashing the system.