The commands are used to clear the Bash history file of the current user, which records the commands entered in the terminal. The first command redirects /dev/null (a special file that discards any data written to it) to temp, which creates an empty file named temp. The second command changes the timestamp of temp to match that of .bash_history (the hidden file that stores the Bash history). The third command renames temp to
.bash_history, which overwrites the original file with an empty one. This effectively erases any trace of the commands executed by the user.
Reference: https://null-byte.wonderhowto.com/how-to/clear-logs-bash-history-hacked-linux-systems-cover- your-tracks-remain-undetected-0244768/