Well after my port blocking escapades of yesterday we have got one complaint.. Someone who was selling exchange based mailboxes. So his /26 is now a permit rule in the acl.. But the blocking, has cut down on our infection rate significantly. (I am seeing a lot of inbound, but not a lot of outbound traffic to 135). mark -- Mark Segal Director, Network Planning FCI Broadband Tel: 905-284-4070 Fax: 416-987-4701 http://www.fcibroadband.com Futureway Communications Inc. is now FCI Broadband -----Original Message----- From: McBurnett, Jim [mailto:jmcburnett@msmgmt.com] Sent: August 12, 2003 12:40 PM To: Jack Bates; Mans Nilsson Cc: nanog@merit.edu Subject: RE: Port blocking last resort in fight against virus Jack, et al. As a larger than average end user and what could be called a small ISP, I really can not image legitimate traffic on 135.. who in there right mind would pass NB traffic in the wild? I dunno, may it is just that Old military security mindset creeping into my brain housing group. Can someone enlighten me? What is legitimate 136 traffic? J -----Original Message----- From: Jack Bates [mailto:jbates@brightok.net] Sent: Tuesday, August 12, 2003 12:31 PM To: Mans Nilsson Cc: nanog@merit.edu Subject: Re: Port blocking last resort in fight against virus Mans Nilsson wrote:
Your chosen path is a down-turning spiral of kludgey dependencies, where a host is secure only on some nets, and some nets can't cope with the load of all administrative filters (some routers tend to take port-specific filters into slow-path). That way lies madness.
Secure? Who's talking about secure? I'm talking about trash. Not blocking the port with a large group of infected users means that your network sends trash to other people's networks. Those networks may or may not have capacity to mean your network's trash. Temporarily blocking 135 is not about security. A single infection within a local net will infect all vulnerable systems within that local net. A block upstream will not save local networks from cross infecting. However, it does stop your network from sending the trash out to other networks which may have smaller capacities than your network does. Of course, perhaps a good neighbor doesn't really care about other people's networks? Perhaps there is no such thing as a good neighbor. It's kill or be killed, and if those other networks can't take my user's scanning them, then tough! There is legitimate traffic on 135. All users I've talked to have been understanding in a short term block of that port. They used alternative methods. I have a lot of valid traffic still cranking out the other Microsoft ports. -Jack