How to assure this secondhand computer ain't hacked?

[simon87]

Hi, just got a computer from secondhand, it has Ubuntu 10 and does not seem to have been used.

If I don't want to reinstall the OS but indeed want to assure that the previous owner are not hacking this computer, what do I need to check?

I just activated Ubuntu firewall (ufw).

What to do next?


Thanks
Simon

[daark.child]

Hi, just got a computer from secondhand, it has Ubuntu 10 and does not seem to have been used.

If I don't want to reinstall the OS but indeed want to assure that the previous owner are not hacking this computer, what do I need to check?

I just activated Ubuntu firewall (ufw).

What to do next?


Thanks
Simon

Hi and welcome to the forum.
You said you do not want to reinstall, but I think its the only way you can be positive that nothing malicious is installed on the system. Activating firewalls does not necessarily help if the system has already been tampered with. If you are adamant you do not want to reinstall, then it maybe a good idea to check for rootkits using something like rkhunter.

[si_ed]

i agree that reinstalling is the only sure way. If that's not an option you might want to monitor the network traffic entering and leaving the suspect system. There are lots of ways to do this. Tcpdump and a hub (not a switch) is possibly the simplest.

[sgosnell]

If you don't want to reinstall the OS then there is no practical way to make sure nothing has been installed. A firewall will do no good, since it only protects against something being installed from outside in the future. You could theoretically go through every directory searching for suspicious files, but that isn't practical, and probably not even effective if you could do it, because it's easy to rename executable files to anything at all. If you're truly worried about the computer being 'hacked', then bite the bullet and reinstall an OS. It doesn't take that long, and Ubuntu 10.something has been superseded anyway.

[MikeTbob]

I agree with all the above. Re-installation is the only failsafe way to do this if you don't trust the person you got it from.

[Hyp0tez]

nodding furiously.
reinstall

[jmadero]

Not sure if you are an experienced linux user or just trying it out now that you have a machine with Linux but "in general" installing Linux (especially Ubuntu) is MUCH easier than Windows. Nothing to be afraid of, if you do it from a USB drive, takes about 15 minutes and you'll have a clean system guaranteed.