Guide: Laptop firewall security

By jobeard
Feb 14, 2007
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  1. If like me, your laptop is your major system, then you might have concerns when
    moving from your home LAN to a public hotspot -- at least I sure do!

    At home, I have a router as a perimeter defense. By avoiding all port forwarding,
    adding MAC filtering for DHCP address assignments, I have a tight environment
    and can allow a visiting friend to hook-up without concern.

    However, at a public hotspot, I do not have control of the router, loose my
    MAC filtering, and get exposed for file/print sharing issues as well as a host
    of known Trojans that visit various specific ports.
    My sole proactive defense becomes the firewall rules.

    My router is on so the whole LAN subnet would normally be -- thru

    I've defined {home-lan} as and
    where MAC filtering ensures only known devices and systems can
    reside in this range. Any visitors will be at and above.
    {home-brdcst} is

    The attachment is a screenshot of my firewall rules and the following text
    explains the usage of each.

    Firewall Rules:

    R0: deny fragmented packets, stopping reassembly attacks
    R1: allow all local services on the loopback interface
    R2: allow all DNS requests
    R3: allow all DNS replies

    allow tcp/udp in/out to ip to port 67 (bootp access)
    allow tcp/udp in/out to ip to port 68 (dhcp access)

    R4: allow LAN-2-LAN access {restricted to}
    R5: allow LAN access to the broadcast address for sharing requests/ print monitoring
    edit: add port 138 to access WORKGROUP names, eg
    ports {137,138,161}
    R6: allow all print sharing
    R7: allow all access to ftp, http sites
    R8: allow all access to smtp, pop3, nttp (ie email + news)
    R9: allow IP Protocol GRE (for VPN access)
    R10: deny rpc queries
    R11: specific site
    R12: windows service in hotspots

    rules for hotspot protection to trojans known on specific ports:
    R13: 1047,1234,1492,1812,1978,1999,2002,2082,2140,2745,2773,2967,3127,3410,4444,5554,
    R14: 6129,6711,6712,6713,6771,7215,7300,7301,7302,7303,7304,7305,7306,7307,7308,8787,
    R15: 4156,8594,9000,9872,9873,9874,9875,9876,9999,
    R16: 17300,27347,31378,36794,

    R17-19: allow ICMP (ie ping)

    R20-22: deny non-routed private networks

    R23: deny everything NOT http (port 80)

    Known Issues:
    Rules 4-5 expose file sharing and everything else on this LAN.
    At a hotspot, this rule would be change to BLOCK or deny access

    Rules 21-22 explicitly block private networks 10.*.*.* and 172.16.*.*,
    one of which would be required to have any access at all.

    Both of these problems could be resolved by a firewall which implements
    the concept of a network profile: rules applied depending upon the specific
    adaptor and/or IP address configured. Norton IS has that feature, but like
    many others, I've elected to dump that product.

    Rules 13-16 are really redundant as rule 23 covers these cases.
    These are known trojan attack ports that would be defacto defeated just by
    the presence of my router. At a hotspot, there are known systems attached
    and I can't assume everyone is well intended.
    Details on Trojan Ports may be found here.

    Personally, I like documentation and this is where I elected to place it.

    Attached Files:

    drensmith likes this.
  2. fyz

    fyz TS Rookie

    It helps me a lot, thanks.
  3. drensmith

    drensmith TS Rookie Posts: 74

    What version do you have? I couldent find that window on my comodo
  4. jobeard

    jobeard TS Ambassador Topic Starter Posts: 11,130   +982

    In the migration to Win/7, I dropped Comodo and opted for the native FW - - it's finally something that can be managed :)
    drensmith likes this.

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