RE: N00b Question
From: Corbett, Tim D. (James Tower) (TDCorbett_at_jamestower.com)
Date: Thu, 6 Jan 2005 12:20:01 -0600 To: "security basics" <email@example.com>
I agree...a packet shaper would be a gross mis-use for simple blocking.
Packet shapers CAN do blocking, but they are better suited for bandwidth
throttling, quality of service, and usage tracking (nor are they
necessarily cheap). We use one here to manage bandwidth for service
agreements for various customers. In this case though, I would do as
Mike suggested and simply create an ACL on your router...
From: Mike [mailto:firstname.lastname@example.org]
Sent: Wednesday, January 05, 2005 11:02 PM
To: security basics
Subject: Re: N00b Question
Since this application only works with standard ports...wouldn't be just
as easy to block those ports at the router?
> There is a great product called packet shaper by packetteer. This
> blocks traffic at the application level. If a user tries to use
> AIM, iTunes, etc... on a different ports or IP's other that the
> ports and IP's this device will detect it. This device detects the
> signatures of these application's packets as they pass through this
> I work of a college and as you can imagen our students ate up our
> with P2P apps, we purchased this device and saved a whole lot of
> I hope this helps.
> On Wednesday 05 January 2005 15:00, Scott Ladd wrote:
>>The method you mention has man flaws, namely, multiple hosts. AIM for
>>instance, uses multiple IP address and ports for connecting. You would
>>have to block an IP Range for that matter. Setting up a firewall is
>>best bet in the end.
>>From: Beauford, Jason [mailto:jbeauford@EightInOnePet.com]
>>Sent: Monday, January 03, 2005 8:30 AM
>>Subject: RE: N00b Question
>>No need to sit there and block ports. Just block access to the hosts
>>these services connect to.
>>For instance I-Tunes: I-Tunes has built in Internet Radio which can
>>suck up my bandwidth. I use Websense to block HTTP and other ports.
>>However, I-Tunes uses a HUGE range of ports. Sure you can block all
>>those ports, but it's just much easier to block the site from which
>>I-Tunes gathers it's XML list of Radio stations. Now the proggie just
>>MSN and Yahoo Chat all connect to some remote host. Install and fire
>>Ethereal on your PC, Install these programs and sign in. Check your
>>Ethereal Logs and you'll easily be able to identify which hosts those
>>programs are connecting to.
>>My $.02. Happy New Year All!
>>From: G.Crow [mailto:email@example.com]
>>Sent: Thursday, December 30, 2004 10:33 PM
>>Subject: RE: N00b Question
>>For blocking certain sites your best bet is a proxy of some sort,
>>presumably transparent. Lots of people on this list will point you
>>towards Squid if you're looking in the open-source realm. You *could*
>>block site IPs in your firewalls (PIX firewalls are almost all, if not
>>all, in the 500-scheme. I haven't looked at the lineup recently.)
>>is, however, not a great solution for a variety of reasons.
>>If you are blocking the web-based email, why do you need to block the
>>ability to upload attachments?
>>For MSN/yahoo chat you can block the ports in your external firewall.
>>This will stop 95% of your users (possibly more if MSN/yahoo don't
>>accept connections on any port like AIM does.) You can also see if
>>infrastructure supports deep packet inspection - Cisco has a good
>>variety of capabilities regarding that, but I can't for the life of me
>>remember the acronym, and my Cisco books are in the office. I avoid
>>myself, since it punts packets to the processor, but that doesn't
>>as much with a slower external link.
>>Quotas established for web surfing? Do you mean accounting per
>>(he's been on the web *this* much today) or do you actually mean
>>it off after a certain point per day? Logging and log analysis is
>>enough, but true quotas would require authentication of some sort most
>>likely, and are probably more trouble then they're worth. If
>>is an issue I would just implement QoS and put port 80/443 traffic in
>>>From: Harshal Dedhia [mailto:firstname.lastname@example.org]
>>>Sent: December 30, 2004 11:42 AM
>>>Subject: N00b Question
>>>I am very new to the firewall and network security world. I have a
>>>situation wherein I need to block webbased email access and the
>>>ability to upload attachments to web-based email. I also need to
>>>ensure that MSN/yahoo chat is disabled and quotas are established for
>>>Is there an Open Source solution to this problem. The network
>>>comprises Cisco Routers and 500 series firewalls.