A computer virus replicates itself by inserting its code into other programs or data files on a computer system, essentially "infecting" them and allowing the virus to spread.
The Replication Process Explained
The replication process of a computer virus mimics, in some ways, a biological virus. Just like a flu virus needs a host cell to reproduce, a computer virus requires a host program or file. Here's a breakdown of the key steps:
-
Attachment: The virus code attaches itself to an executable file (like a .exe or .com file) or a document with embedded macros. This could be through directly modifying the file's contents or by creating a new file that mimics the original.
-
Activation: The virus remains dormant until the infected program is executed or the infected document is opened. This action activates the virus code.
-
Replication: Once activated, the virus begins searching for other potential hosts (other programs or documents) on the computer system or network.
-
Infection: The virus copies its code and inserts it into these new host files, thereby infecting them. This process repeats each time an infected program is run or a document is opened.
-
Execution: After replicating, some viruses will also perform malicious actions, such as deleting files, corrupting data, stealing information, or displaying unwanted messages. However, the primary function is always replication.
Analogy to Biological Viruses
| Feature | Computer Virus | Biological Virus |
|---|---|---|
| Purpose | Replicate and spread to other systems | Replicate and spread to other hosts |
| Host | Executable files, documents, boot sectors | Living cells |
| Replication Mechanism | Attaching code to executable files/documents | Inserting genetic material into host cells |
| Activation | Executing infected program/opening document | Contacting a host cell and injecting its genetic material |
Methods of Propagation
Computer viruses can spread through various methods, including:
- Email attachments: Infected files sent as attachments.
- Infected websites: Downloading infected software or visiting compromised websites.
- USB drives: Copying infected files to and from removable storage.
- Network shares: Spreading through shared folders on a network.
- Software vulnerabilities: Exploiting weaknesses in software to inject malicious code.
Example
Imagine a file named "myprogram.exe" that becomes infected. When you run "myprogram.exe," the virus activates. It then searches your computer for other .exe files. When it finds another program like "game.exe", it modifies "game.exe" to include a copy of the virus code. Now, when you run "game.exe," it also activates the virus and the replication process continues.
