similar to: forwarded from BoS: Linux anti-SYN flooding patch

Hi *Problem *- I'm running Icecast in a VM container on OpenVZ. Syslog on the hardware node (HN) shows these error messages: Jan 23 18:43:05 HN kernel: [27469893.430615] possible SYN flooding on port 8000. Sending cookies. Jan 23 21:37:40 HN kernel: [27480362.817944] possible SYN flooding on port 8000. Sending cookies. Jan 23 23:43:50 HN kernel: [27487929.582025] possible SYN flooding on

On 07/20/2018 03:56 AM, Leon Fauster via CentOS wrote: > Hi folks, > > I have here a database node running > > # rpm -qa | grep mysql-server > mysql55-mysql-server-5.5.52-1.el6.x86_64 > > on > > # virt-what > vmware > > > that seems to have a connection problem: > > # dmesg |grep SYN |tail -5 > possible SYN flooding on port 3306. Sending cookies.

Anyone seen this problem? server Apr 16 14:34:28 nas1 kernel: [7506182.154332] TCP: TCP: Possible SYN flooding on port 49156. Sending cookies. Check SNMP counters. Apr 16 14:34:31 nas1 kernel: [7506185.142589] TCP: TCP: Possible SYN flooding on port 49157. Sending cookies. Check SNMP counters. Apr 16 14:34:53 nas1 kernel: [7506207.126193] TCP: TCP: Possible SYN flooding on port 49159. Sending

On a Linux Server running tincd I noticed the following log message in /var/log/messages kernel: possible SYN flooding on port 655. Sending cookies. I found this on the web: If SYN cookies are enabled, then the kernel doesn't track half open connections at all. Instead it knows from the sequence number in the following ACK datagram that the ACK very probably follows a SYN and a SYN-ACK.

Hello, I current have a FreeBSD 4.8 bridge firewall that sits between 7 servers and the internet. The servers are being attacked with syn floods and go down multiple times a day. The 7 servers belong to a client, who runs redhat. I am trying to find a way to do some kind of syn flood protection inside the firewall. Any suggestions would be greatly appreciated. -- Ryan James ryan@mac2.net

Hi folks, I have here a database node running # rpm -qa | grep mysql-server mysql55-mysql-server-5.5.52-1.el6.x86_64 on # virt-what vmware that seems to have a connection problem: # dmesg |grep SYN |tail -5 possible SYN flooding on port 3306. Sending cookies. possible SYN flooding on port 3306. Sending cookies. possible SYN flooding on port 3306. Sending cookies. possible SYN flooding on

Hello *, I've the following problem with dovecot 1.0.7: /var/log/messages shows | Dec 13 13:48:27 mailbox kernel: possible SYN flooding on port 143. Sending cookies. and /var/log/maillog shows (Please note: nearly the same time): | Dec 13 13:48:28 mailbox dovecot: pipe() failed: Too many open files This leads to an unresponsive mail service and requires a dovecot restart. What

> Am 20.07.2018 um 18:52 schrieb Nataraj <incoming-centos at rjl.com>: > > On 07/20/2018 03:56 AM, Leon Fauster via CentOS wrote: >> Hi folks, >> >> I have here a database node running >> >> # rpm -qa | grep mysql-server >> mysql55-mysql-server-5.5.52-1.el6.x86_64 >> >> on >> >> # virt-what >> vmware >>

-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-02:20 Security Advisory FreeBSD, Inc. Topic: syncache/syncookies denial of service Category: core Module: net Announced: 2002-04-16

Default,syncookies are activate when syn list(backlog queue) is full. I want hybrid system. I propose a system , syncookies active dynamic per connection . where will I write code , where syncookies system does call in the code file.

-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-96.21 Original issue date: September 19, 1996 Last revised: -- Topic: TCP SYN Flooding and IP Spoofing Attacks - ----------------------------------------------------------------------------- *** This advisory supersedes CA-95:01. *** Two

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ______________________________________________________________________________ Caldera International, Inc. Security Advisory Subject: Linux - syncookies firewall breaking problem Advisory number: CSSA-2001-038.0 Issue date: 2001, November 05 Cross reference: ______________________________________________________________________________ 1.

Hi, folks @ freebsd-security. First, I am not sure if this is apropriate topic for that list, so sorry, if it is not. Some time ago I have read rfc1948 (protection from blind TCP spoofing) and became interested in the way how it is implemented in FreeBSD. After some googling (BTW if you like Google you might be interested in this: http://register.spectator.ru/img/bart.gif ), I found this:

--------------------------------------------------------------------- Red Hat, Inc. Red Hat Security Advisory Synopsis: kernel 2.2 and 2.4: syncookie vulnerability Advisory ID: RHSA-2001:142-15 Issue date: 2001-10-26 Updated on: 2001-11-02 Product: Red Hat Linux Keywords: syncookie security kernel Cross references: Obsoletes:

Hi, I got this error when i tried to type for some of those. "sysctl: unknown oid...." any idea.. my server seems to be very lagged, where else the network connection seems fine, i think BSD itself as my other redhat box is fine. What else can i do to get optimum protection. Thanks. ----- Original Message ----- From: "Per Engelbrecht" <per@xterm.dk> To:

Heya, FREEBSD 4.9-STABLE Is there anyway to block SYN attacks and prevent it from bring down my server? Its been attacking for sometime.

Hallo Group, i want to implement a syn Flood Protection on our linux Router. on our Cisco we have this Access-list and rat-limit rate-limit input access-group 190 128000 128000 128000 conform-action transmit exceed-action drop access-list 190 deny tcp any any established access-list 190 permit tcp any any access-list 190 deny ip any any now i was trying to wrote the same config with

Perhaps someone will help me on this :- I have read a lot of examples of syn flood protect on the INPUT chain. That I have no question at all. I wonder if it make sense to perform syn flood protection at the FORWARD chain ? If packets are originated from a LAN worm, and are not targetted at the firewall itself, but rather at hosts in the internet, will it cause problem with the firewall itself,

Hello Stephen, I may have tracked down some unexpected behaviour from a common bridge setup, and would like to incite expert oppinion on my observations. The issue relates to both 2.6 and 2.4 kernel series bridging code, and as far as I can see might have been present in all releases hitherto. Consider this setup: - two ethernet devices in a simple bridge configuration - bridge-interface

Hello everyone, is a pleasure to be here. I have a problem with my server, it runs qmail SMTP and protect it with shorewall. Since yesterday I get syn flood attacks on port 25, which means that no longer meet. How can I stop this with shorewall? my setup is as follows. zones: #ZONE DISPLAY COMMENTS net Net Internet loc Local Local networks dmz DMZ