How to replace the top shell script?

Question

Can the top command in /usr/bin be replaced? I read on superuser that it can hide processes if compromised. I want to delete top and get a fresh new script using apt-get from Ubuntu official repositories.

Answer 1

top is a part of procps package you can reinstall it using:

sudo apt install --reinstall procps

or install a version from a repository which you trust, run apt-cache policy proccps, which outputs:

procps:
  Installed: 2:3.3.10-4ubuntu2.3
  Candidate: 2:3.3.10-4ubuntu2.3
  Version table:
 *** 2:3.3.10-4ubuntu2.3 500
        500 http://mirrors.kernel.org/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2:3.3.10-4ubuntu2 500
        500 http://mirrors.kernel.org/ubuntu xenial/main amd64 Packages

pick a version from a repository which you trust and specifically install that one:

sudo apt remove procps
sudo apt install procps=2:3.3.10-4ubuntu2.3

You can also check and see if this file is compromise using dpkg -V:

run:

dpkg -V procps

If top has been compromised it will show you an output look like:

??5??????   /usr/bin/top

otherwise it show nothing.