search for: syn

Near the end of section 15.10, the following commands are shown for prioritizing SYN packets: iptables -t mangle -I PREROUTING -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -j MARK --set-mark 0x1 iptables -t mangle -I PREROUTING -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -j RETURN Shouldn''t the "-I" option really be "-A"? Like so: iptables -t man...

Hello Everyone, I have 2 different suggestions about syn-cookies method which is used to block syn-flood attacks. Syn cookies bitwise image --------------------------------------------- T(5 bits) ---MSS(3 bits)-----H(24 bits) --------------------------------------------- So, 1- T value can be decreased to 2 bit which is already 5 bit.And hash value...

...thing, I discovered right now... > Could you suggest me something to restrict the problem? > Currently, I think the problem can be: > > 1) on Asterisk > 2) on my Gateway/Firewall A couple of years ago I added this entry in my firewall: /sbin/iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu since I had the problem downloading data from an Internet site using my tablet. I found this site explaining that: https://lartc.org/howto/lartc.cookbook.mtu-mss.html I really forgot this entry, but now I checked all entries in my Firewall, and I see...

...uch connections? I notice in the FAQs that Instant Messenger requires a UPnP add-on, but my understanding of UPnP is that it''s somewhat different than what I''m trying, so I''m not sure whether this is a similar case. Basically, if the machine behind Shorewall sends out a [SYN] message but Shorewall then receives a [SYN] from the target rather than a [SYN, ACK], would you expect Shorewall to block the [SYN] message or allow it through? Is it possible for Shorewall to block messages without logging it in any way, assuming maximum logging is switched on? An illustration...

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 wi...

...y for each view select column_name, data_type, data_default, nullable, decode(data_type, ''NUMBER'', data_precision, ''VARCHAR2'', data_length, null) as length, decode(data_type, ''NUMBER'', data_scale, null) as scale from user_catalog cat, user_synonyms syn, all_tab_columns col where cat.table_name = ''USERS'' and syn.synonym_name (+)= cat.table_name and col.table_name = nvl(syn.table_name, cat.table_name) and col.owner = nvl(syn.table_owner, user) I am assuming that this is because development mode can''t cache t...

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 port 3306. Sending cookies. possible SYN flooding on port 3306. Sending cookies. I adapted already follo...

Hi, First of all, I know that not dropping SYN/FIN isn't really a big deal, it just makes no sense. But since it doesn't make any sense, I don't see the reason why not to discard them. I'm running pf on FreeBSD 5.4-RELEASE-p3 and I scrub any traffic. I've read some other posts on google and as far as I can tell, clearly inv...

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 *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 port 8000. Sending cookies. Jan 24 00:27:34 HN kernel: [27490551.695794] possible SYN flood...

Hi, after some experience with Rails on MySQL databases I gave it a try on one of our larger Oracle database. I was facing a problem when Rails tried to detect the columns for a model/table. The appropriate statement ran about 1 min which led to a timeout. Our Oracle guru told me to analyze the SYSTEM schema. After that hadn''t helped, he said the only remaining chance is to use a

...for that, that''s really helped. Netfilter is indeed dropping the packets as invalid. Thanks and regards, Frances -----Original Message----- From: Tom Eastep [mailto:teastep@shorewall.net] Sent: 23 March 2007 18:05 To: Shorewall Users Subject: Re: [Shorewall-users] Expected handling of [SYN] when expecting[SYN, ACK]? Frances Flood wrote: > Basically, if the machine behind Shorewall sends out a [SYN] message > but Shorewall then receives a [SYN] from the target rather than a > [SYN, ACK], would you expect Shorewall to block the [SYN] message or > allow it through? Fir...

...ere 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 port 3306. Sending cookies. >> possible SYN flooding on port 330...

Hi, sorry to bother you, and that this is probably not the right list :-), but I read that some of you might use syn as Editor for .R files. I've released an unofficial Version of the syn Text Editor with improved support for R (I'm the initial developer of this program, btw.). syn is a Windows 32 Program (Win9x, NT4, 2000), but maybe it runs also inside Wine, I didn't try it. Improved means: - More...

Here's the output: Feb 9 15:51:26 SSI001 kernel: SFW2-INext-ACC-TCP IN=eth0 OUT= MAC=00:0f:ea:73:88:12:00:40:2b:67:5b:a7:08:00 SRC=192.168.1.54 DST=192.168.1.2 LEN=48 TOS=0x00 PREC=0x00 TTL=128 ID=51248 DF PROTO=TCP SPT=1964 DPT=139 WINDOW=65535 RES=0x00 SYN URGP=0 OPT (020405B401010402) Feb 9 15:51:28 SSI001 kernel: SFW2-INext-ACC-TCP IN=eth0 OUT= MAC=00:0f:ea:73:88:12:00:12:3f:a1:fd:1b:08:00 SRC=192.168.1.61 DST=192.168.1.2 LEN=48 TOS=0x00 PREC=0x00 TTL=128 ID=2065 DF PROTO=TCP SPT=1136 DPT=445 WINDOW=65535 RES=0x00 SYN URGP=0 OPT (020405B401010402...

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.

Hi, I''m interested in prioritizing all packets with the SYN bit on, both with and without the ACK bit on (but specially the SYN ACKS). I am checking is the use of Diffserv. From a paper I read I understood that when Diffserv is on, all "Control Traffic", including TCP SYN-ACKs, gets by default into "band 0" of Diffserv, the highest pri...

...enhance it. First of all, I need to reproduce in R the results which were already obtained in Matlab (to make sure that everything is correct). There are some matrix manipulations and '\' operation among them in the code. I have the following data frame > ABS.df Pro syn unk Chl Y Nh V1 1 0.056524968 0.04387755 -0.073925372 0.026477146 0.083527021 0.0031950622 0.02164793 2 0.066456284 0.05992579 -0.094609497 0.031772575 0.054881164 0.0022078221 0.01358594 3 0.036383887 0.04601113 -0.06121...

...Shorwall Development list since I believe that these issues will be of interest. On Tue, 6 Aug 2002, Links at Momsview wrote: > Tom, > I''m not sure if you ever saw this document but it describes some of the > reasons you are seeing strange packets > after setting up NEW not SYN > http://www.linuxsecurity.com/resource_files/firewalls/IPTables-Tutorial/ipta > bles-tutorial.html#NEWNOTSYN > Thanks. > > I didn''t notice where the actual ACCEPT was for these connections but I > assume they are on a Port by port basis. > Yes. > PS: I belie...

...unbreakable. ;--------------------End clipboard---------------------------- In the diff to previous revision: http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_subr.c.diff?r1=1.73.2.21&r2=1.73.2.22 is said: ;------------------Begin clipboard---------------------------- + * The ISNs in SYN-ACK packets have no monotonicity requirement, + * and should be as unpredictable as possible to avoid the possibility + * of spoofing and/or connection hijacking. To satisfy this + * requirement, SYN-ACK ISNs are generated via the arc4random() + * function. If exact RFC 1948 compliance is request...