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Thread: What is the purpose of a firewall?

  1. #1
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    What is the purpose of a firewall?

    I'm just wondering, I like to use my laptop at Starbucks once in a while. I'm running Ubuntu 13.04 with Cinnamon.

    I haven't created any shared folders on my computer (mostly because I don't know how ), but would I need to run a firewall and if so why? I know I have GUFW but it is not enabled.

    Thank you

  2. #2
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    Re: What is the purpose of a firewall?

    A firewall blocks incoming connections.

    There are two services running on Ubuntu by default that listen for incoming local network connections (not from the internet, though). It's possible that a savvy attacker in the same Starbucks could open a connection to one of those services on your computer, and use an unreported security vulnerability in that service to run code on your computer.

    It is very improbable, but it is possible. If you use a firewall that blocks all incoming ports to your computer, you can completely avoid such an attack.

  3. #3
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    Re: What is the purpose of a firewall?

    I think, this sticky http://ubuntuforums.org/showthread.php?t=1871177 can answer your question.

  4. #4
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    Re: What is the purpose of a firewall?

    a firewall restricts access to your computer from outside. iptables/netfilter is the firewall built into the linux kernel, and UFW, GUFW, etc are the most commonly used tools to modify iptables by people that don't know iptables (or prefer the simplicity). UFW is a good starting point, but it's a good idea to know iptables just in case, however, your mileage will vary. if you don't have Samba shares then the most common island hop is closed, however, it's always a good idea to learn about your security, especially for publically accessable devices.

  5. #5
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    Re: What is the purpose of a firewall?

    As I understand it the problem is not so much someone getting into your PC but rather intercepting your traffic.
    The bad guy would be sitting in Starbucks and create an ad-hoc wifi network on his laptop called "Starbucks supafast" for example. Not knowing that this is a phoney network you connect to it and he can catch your login details and cookies when you sign in to your bank or social network.
    That is why people use VPNs, it would "tunnel" through the phoney network and connect to the internet at a trusted location.
    I am not an expert in this field so you might want to do some more research or start another thread.

  6. #6
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    Re: What is the purpose of a firewall?

    Quote Originally Posted by HiImTye View Post
    if you don't have Samba shares then the most common island hop is closed, however, it's always a good idea to learn about your security, especially for publically accessable devices.
    While I haven't created any shares myself, is there a command that I can run to see if there are any shares that exist on my system?

  7. #7
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    Re: What is the purpose of a firewall?

    you can see if the Samba daemon is running
    Code:
    ps -ef | grep smbd
    @coldraven, you can sniff out unencrypted wifi traffic by using your adapter in monitor mode as well. best practices are to always use SSL when on wifi

  8. #8
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    Re: What is the purpose of a firewall?

    Quote Originally Posted by HiImTye View Post
    you can see if the Samba daemon is running
    Code:
    ps -ef | grep smbd
    @coldraven, you can sniff out unencrypted wifi traffic by using your adapter in monitor mode as well. best practices are to always use SSL when on wifi
    I ran this command from terminal and received the below response. Could you tell me what this means?

    1645 1569 0 22:36 pts/0 00:00:00 grep --color=auto smbd

  9. #9
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    Re: What is the purpose of a firewall?

    Quote Originally Posted by carmen2012 View Post
    1645 1569 0 22:36 pts/0 00:00:00 grep --color=auto smbd
    that's the
    Code:
    grep
    command searching for the string you gave it (smbd). if smbd was running you would have seen entries like this
    Code:
    root <some numbers> <start time> ? <cpu time> smbd -F
    as well as the entry above. if you don't want to see grep in the ps output then you would grep -v it, such as
    Code:
    ps -ef | grep smbd | grep -v grep
    hope this helps!

  10. #10
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    Re: What is the purpose of a firewall?

    Can't believe nobody said it so far, but a firewall prevents unauthorized traffic, both inbound and outbound. People don't seem to understand that if somebody gets in, they could do all sorts of nasty things from your box, like installing their own software and attacking another box, or communicating with whatever the bad guys are using to do what they do.

    Something like http or https is going to be tough to limit, but you could easily limit the types of queries that can go out without affecting your personal use of your computer.

    You could also limit access of those shares based on one or two single IP addresses that you have at home, which would reduce the likelihood that the Starbucks attacker would be able to get in.

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