nobody (username)

In many Unix variants, "nobody" is the conventional name of a user account which owns no files, is in no privileged groups, and has no abilities except those which every other user has.

It is common to run daemons as nobody, especially servers, in order to limit the damage that could be done by a malicious user who gained control of them. However, the usefulness of this technique is reduced if more than one daemon is run like this, because then gaining control of one daemon would provide control of them all. The reason is that nobody-owned processes have the ability to send signals to each other and even (on Linux) ptrace each other, which means that one process can read and write to the memory of another process. Creating one account for each daemon, as recommended by the Linux Standard Base,^[1] provides for a tighter security policy.

See also

• Principle of least privilege
• Privilege revocation

References

1. ^ Linux Standard Base, Core Specification 3.1 section 21.2: User & Group Names, freestandards.org