bash Cookbook

Clearing All Aliases

Problem

You need to make sure that there are no malicious aliases in your environment for security reasons.

Solution

Use the \unalias-a command to unalias any existing aliases.

Discussion

If an attacker can trick root or even another user into running a command, they will be able to gain access to data or privileges they shouldn’t have. One way to trick another user into running a malicious program is to create an alias to some other common program (e.g., ls).

The leading \, which suppresses alias expansion, is very important because without it you can do evil things like this:

$ alias unalias=echo
$ alias builtin=ls

$ builtin unalias vi
ls: unalias: No such file or directory
ls: vi: No such file or directory

$ unalias -a
-a

See Also

• Redefining Commands with alias

• Avoiding Aliases, Functions

• Shortening or Changing Command Names