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My question may seem very amateurish or even incorrect, but do please take in account that I'm a complete noob in computer and network security. I'm just trying to find out some information here.

Most users do use quite weak passwords for their home systems, many of them actually do use the same password for root/mail/forum/social network accounts, and its a fact. So, bearing this in mind, is it easy to hack a computer of such a user? A hacker finds his IP address (just a random pick I guess) and then decides to crack it. Will it be easy or not? How much time will it take? And how difficult will it be to hack a strong passworded PC? Maybe a good hacker will not need a password at all, I don't know. As I mentioned above, I don't yet understand all the ins and outs of networking.

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A hacker is not going to be able to access your computer unless you have software that allows him to access running or there is an exploit in a service that exposes you to the internet. Everything you seen about hacking in the movies is 100% fake. Besides the fact most people are behind a router or at least a modem that behaves like a firewall most security events like you attempt to describe are because of an exploit in the operating system itself. You having a weak password is not a concern of those types of criminals. –  Ramhound Jan 6 '12 at 16:46
    
thank you for your answer. –  tasty_minerals Jan 6 '12 at 16:56

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up vote 7 down vote accepted

If a computer in question is running SSH or FTP or other service that allows remote login, and access to that service is not blocked in the firewall, and not prevented due to NAT (e.g. the PC is behind a home router), then that PC can be hacked remotely, just by trying passwords one after another.

Most online servers that I audit receive constant SSH "hacking" attempts (e.g. some zombie PC is trying "admin/admin" and other similar "weak" username/password combinations, therefore if you use something that weak, your PC will be hacked sooner than later (if SSH can be accessed remotely, of course).

If your password is at least somewhat complex, than it can be hacked only by dedicated effort, not by "drive-by" hacking.

However, most security professinals believe in "defence in depth", e.g. you must have several layers of defence: firewall, strong passwords or certificate-only auth, regular audits, etc. Therefore, if one of the security layers is compromised (say, you botched your firewall config), you're still safe as other layers of protection defend your computer from hacking.

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Yes, "defence in depth", I've met this terminology in some papers on information security, thank you) –  tasty_minerals Jan 6 '12 at 16:59
    
@haimg - I think its fair to point out the author appears to be talking about a home linux pc. My comment trying to explain these criminals do not attempt to scan for victims, in order to "access" their computer as shown in the movies, now shoving malware at them is entirely different through an exploit in a service or operating system feature. As you point out a server that likely has a static address is much more likely to be attacked, and one could argue, its just a matter of time until they are. A home user despite a few exceptions in the early life of Windows XP its just unlikely. –  Ramhound Jan 6 '12 at 17:01
    
@Ramhound: Criminals (their zombies in botnets) do scan whole subnets (including residential broadband) for victims (weak SSH username/password pairs). Static address have nothing to do with it. If you're behind NAT, you're reasonably secure, but being a "desktop" PC does not somehow magically protect you or make you a lesser target for drive-by hacking. –  haimg Jan 6 '12 at 17:08
    
Re SSH. Only allow public-key authentication and disallow password based authentication (from at least off-LAN clients). This prevents password guessing. –  RedGrittyBrick Jan 6 '12 at 17:09
    
Yes, I was talking about a mere user. Server is completely another story, I guess. –  tasty_minerals Jan 6 '12 at 17:09

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