Nmap Announce mailing list archives
Re: (local?) linux DoS using nmap
From: "Mr. Man" <mrman () darkside org>
Date: Thu, 3 Jun 1999 01:08:27 -0500 (CDT)
What kernel version are you running, and do you have SYN Cookies enabled in that kernel? Also, were all the other services that died being called from the inetd superserver? Inetd may have died, which I think might have been a previous problem with nmap and some versions of inetd. I'm not sure which inetd is shipping with those distributions these days, but it'd be best to use an inetd that limits the amount of commections for each type of service per IP address. The inetd that ships with my slackware 3.4 box has this option: -q queuelength Sets the size of the socket listen queue to the specified value. Default is 128. Adjusting the queue size one way or the other may help stop the problem. FreeBSD's inetd has the following options which I'm not sure these distributions have. They are: -c maximum Specify the default maximum number of services that can be in-voked. May be overridden on a per-service basis with the "max-child" parameter. -C rate Specify the default maximum number of times a service can be in-voked from a single IP address in one minute; the default is un-limited. May be overridden on a per-service basis with the "max-connections-per-ip-per-minute" parameter. -R rate Specify the maximum number of times a service can be invoked in one minute; the default is 256. I hope that sheds some light on the problem. I'm pretty sure inetd has just died, which causes all services normally called form it (ftpd, telnetd, etc.) to fail. Mr. Man - Darkside Labs If at first you don't succeed, destroy all evidence that you tried. On Thu, 3 Jun 1999, cami wrote:
Good day.. I appologize if this is old but seems still to be working/active on my own server. (slackware 4.0.0). I would be interested to know which other distro's this works against. Tested against: slackware 4.0.0 debian 2.1 Redhat 6.0 I became aware of this when local users begun to launch DoS attacks. kernel:~$ nmap 127.[0-255].[0-255].[0-255] -p 21 -sT Starting nmap V. 2.12 by Fyodor (fyodor () dhp com, www.insecure.org/nmap/) Interesting ports on localhost (127.0.0.1): Port State Protocol Service 21 open tcp ftp Interesting ports on (127.0.0.2): Port State Protocol Service 21 open tcp ftp <snip> and it keeps going untill the +/-280th packet.. <snip> Interesting ports on (127.0.1.32): Port State Protocol Service 21 open tcp ftp No ports open for host (127.0.1.33) No ports open for host (127.0.1.34) No ports open for host (127.0.1.35) etc.. etc.. <snip> I havent tested it on remote machines, but this looks like a tcp/syn flood? Anyhow, local users can shutdown any local daemon running on any port. (apache was the only service that remaining running.) The rest of the other services became unusable/(dead?). Any ideas how one could prevent this? Sorry again if this is old. Regards hotmetal of (src) hotmetal () hack co za ( www.hack.co.za ) (e x p l o i t m a t r i x) (world domination in progress)
Current thread:
- (local?) linux DoS using nmap cami (Jun 02)
- Re: (local?) linux DoS using nmap Mr. Man (Jun 02)
- Re: (local?) linux DoS using nmap Vidyut Luther (Jun 03)
- <Possible follow-ups>
- Re: (local?) linux DoS using nmap cami (Jun 03)
- Re: (local?) linux DoS using nmap Lamont Granquist (Jun 03)
- Re: (local?) linux DoS using nmap Ken Williams (Jun 05)
- Re: (local?) linux DoS using nmap moses (Jun 06)
- Re: (local?) linux DoS using nmap Mr. Man (Jun 02)