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Let me first admit that I am a nobody in computer security - I just know the various threats generally known to public.

I have a Linux Cent OS 7 installed on my computer which is connected to the Internet always - on my personal home network.

I download a lot of stuff like linux softwares, jar files, images, movies etc from the internet.

My question is : Just by connecting to the internet, is it possible for an outsider to steal my files ? Well I know that it is theoretically possible, but I want to know what the outsider will have to do to "Steal" my files - especially when the linux computer is SE Linux enabled with "enforcing" option and the firewall is on.

How easy or hard it is to do this for an outsider ( a remote computer user who is NOT on my network ?

( But i don't know more about the firewall configuration. )

And if you can guide me on any tools available to prevent any of such attacks it would be a real favor.

Thanks in advance.

kausDix75
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3 Answers3

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There is no easy answer to this. Some loose thoughts:

Is this system directly connected to the internet, or is there a router and or firewall between this system an the internet?

How strong are your passwords?

Is your filesystem encrypted?

Do you have ssh login enabled? If so, from where?

Do you use twofactor authentication (google authenticator is free and very simple to implement)

What services does this system run which are listening to connections from the internet?

You could do some pen testing yourself (https://www.kali.org)

Who else has access to this computer?

Is your system up to date?

Are you browsing potentially harmful websites?

sam phunkey
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  • Thanks a lot for answering and the questions. My passwords are strong, filesystem is NOT encrypted, ssh is enabled ( dont know what you mean by from where ) I will give a try to Google Authenticar and the Kali Linux. Nobody else has access to my computer. System is uptodate. Not sure which are potentially harmful websites but generally i visit only tech sites like this one - where i can learn more stuff about computers and programming. – kausDix75 Nov 07 '15 at 07:53
  • About router : are you referring to a Network Router ? if yes then i have one which is provided by my ISP. If not could you please explain what do you mean by that ? Thanks in advance again – kausDix75 Nov 07 '15 at 07:59
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Just going to say a few things and hopefully some of it will provide clarification for you. Whether or not the file system is encrypted makes no difference if it is online 24/7. Running an SSH server can be risky if you haven't restricted access to it (what I think sam meant by the "from where") via your firewall. Additionally, since you are behind a router if you haven't forwarded the ports for the SSH server you will be fine. This assumes however that you are only using SSH to connect from other machines on your local network. If you are going to be accessing the system from remote locations you will need to first set the appropriate rules in your firewall by means of "whitelisting" the IP addresses and block everything else.

In order for someone to gain access to your system they'll need something to attack - these days it often means going for the web browser, so it might be beneficial to use an extension like NoScript which basically acts like a firewall for your browser in that it won't allow scripts (a common delivery method for exploits) to run without your permission.

As for learning things about computers and programming that is a difficult question to answer. There are a ton of resources out there so I cannot really point you to one particular place. I would recommend figuring out what kinds of things you wish to program and then researching languages that would suit your needs. General computer knowledge is acquired over time and some of the most valuable things you'll learn will not be planned or come from a book.

So again, it is going to require a lot of effort for someone to remotely steal your files. You would generally either have to mess up and get tricked into installing spyware or a backdoored piece of software, visit a compromised or dodgy site and have your browser exploited, or leave the door wide open by means of a poorly configured or insecure network service.

Hope this helps.

Jake
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Just by connecting to the internet, is it possible for an outsider to steal my files ?

If you have any internet facing services on your computer (SSH, web server, FTP..) then a simple connection to the internet might be enough to steal data, depending how secure these services are setup.

If you don't have such services the connection to the internet alone is not enough, but simple web browsing might be. Linux is also affected by various commonly used exploits using Java or Flash-Plugin and attacks like CSRF against your router are independent from the OS and even SE Linux can not stop these.

And if you can guide me on any tools available to prevent any of such attacks it would be a real favor.

Basic security things like not having Flash or Java plugin, using Adblocker against malvertising, having the router secured... - nothing much specific to Linux. If you expect more details please ask specific questions, otherwise expect the question to be closed as too broad.

Steffen Ullrich
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