Re: SNMP security issues in D-Link DSL Broadband Modem/Router

From: Maslov, Snowy (Snowy.Maslovat_private)
Date: Fri Mar 28 2003 - 00:18:22 PST

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    > From: Arhont Information Security [mailto:infosecat_private] 
    > Sent: Friday, March 28, 2003 1:32 AM
    > To: bugtraqat_private
    > Subject: SNMP security issues in D-Link DSL Broadband Modem/Router
    >
    > While performing a general security testing of a
    > network, we have found several security vulnerability
    > issues with the D-Link DSL Broadband Modem DSL-500
    
    Note that there are a couple of things you can do to alleviate this
    problem.
    
    1.  Change the public and private SNMP community strings.   You can do
    this by logging into the DSL router via telnet or using the serial
    connection and typing the following (the password for telnet by default
    is 'private' - see below):
    
    snmp access flush                       # Flushes all access strings
    snmp access read <password>             # Sets your RO community
    password
    snmp access write <password>            # Sets your R/W community
    password
                                            # NOTE: This is also your telnet
                                            # password!  Make sure it is
    kept
                                            # safe!
    snmp access list                        # Always good to check ;)
    config save                             # Saves configuration
    restart                                 # Restarts router.
    
    I would really recommend doing this as a matter of course anyways.
    
    2.  You can use the built-in IP filter package to remove access from the
    WAN side to TCP and UDP port 161 (and if you are not using it on the LAN
    side - I'd do the same there too).
    



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