There are proof of concept projects but I am not aware of any actual attacks directly related to the operating system.
Admin password is always required to install anything on Linux, so if you have a weak one maybe best to strengthen it.
If you are really paranoid you can install Sophos Antivirus and clamAV, both free. I never used them. Sophos is supposed to use very little resources.
If you are running a Linux server I would use Sophos as it addresses a vulnerability with compromised OpenSSH servers. Again somebody would have had to have Admin access to compromise it.
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