Security Basics mailing list archives
RE: weird
From: "Hagen, Eric" <ehagen () DenverNewspaperAgency com>
Date: Mon, 23 Feb 2004 17:33:30 -0700
It could be a link-layer DOS attack against your network. It could also be a defective network card that is intermittently flooding the link-layer with random (or even non-random) Ethernet frames. Keep the sniffer running. Take a look at the source MAC address and maybe you can find where it's coming from. Eric -----Original Message----- From: kenzo [mailto:kenzo_chin () hotmail com] Sent: Thursday, February 19, 2004 7:15 PM To: security-basics () securityfocus com Subject: weird This weird thing happened at work. Everything was fine, then all of sudden the whole network freezes. All the swicthes and hub lights are blinking like there's no tomorow. So much traffic going on I can't even ping the computer accross me on the same switch. Then it stops and everything is back to normal. That happened twice. I use Ntop to watch for protocol usage to find infected computers(when that happens) and people using other protocols that the're not suppose to. When this happens the box crashes. I tried using ethereal to see if I saw anything but of course it doesn't happen when I'm ready for it. I looked thru the traffic that I gathered from ethereal but none seem to really stick out. I'm not an expert, so the only thing that I know that will do the same thing is flooding the network with ramdom MAC addresses. Or maybe a major arp flooding or something. I haven't tried the arp flooding, but I know that the Mac flooding does the same thing. What could it be? Did someone flood the network on purpose? If so, how do I track it? Or could it be that a bad Nic or device on the network just went crazy for a while. (That's what my boss seems to think.) Even then, how do I track it? Thanks. --------------------------------------------------------------------------- Free trial: Astaro Security Linux -- firewall with Spam/Virus Protection Protect your network with the comprehensive security solution that integrates six applications for ease of use and lower TCO. Firewall - Virus protection - Spam protection - URL blocking - VPN - Wireless security. Download 30-day evaluation at: http://www.securityfocus.com/sponsor/Astaro_security-basics_040219 ---------------------------------------------------------------------------- --------------------------------------------------------------------------- Free trial: Astaro Security Linux -- firewall with Spam/Virus Protection Protect your network with the comprehensive security solution that integrates six applications for ease of use and lower TCO. Firewall - Virus protection - Spam protection - URL blocking - VPN - Wireless security. Download 30-day evaluation at: http://www.securityfocus.com/sponsor/Astaro_security-basics_040219 ----------------------------------------------------------------------------