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Special Forums Cybersecurity Continual knocking on port 443 from foreign IP address Post 302893863 by Perderabo on Friday 21st of March 2014 11:26:36 AM
Old 03-21-2014
Quote:
Originally Posted by randomxs

Why would someone continually try to access the https port for months on end 100s of times an hour when clearly they must see they are being denied access to the server?


Iptables is not perfect and even when you use DROP rather than REJECT a port scanner can tell that DROP is in use by doing a SYN scan. If a server is on the port the SYN will get an ACK, otherwise it gets a RST. So the bad guy knows that he is getting nailed by a DROP rule and there is a live server being protected by the DROP rule. So he sets up an infinite loop trying to connect.

He hopes you will someday have a problem, wonder if iptables is causing it, and try dropping iptables just for a few seconds. Or maybe you will change your configuration and do a quick "service iptables restart". Most iptable configs allow ESTABLISHED connections to persist so once he connects... he is in.
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IPTABLES-XML(1) 						  iptables 1.4.21						   IPTABLES-XML(1)

NAME
iptables-xml -- Convert iptables-save format to XML SYNOPSIS
iptables-xml [-c] [-v] DESCRIPTION
iptables-xml is used to convert the output of iptables-save into an easily manipulatable XML format to STDOUT. Use I/O-redirection pro- vided by your shell to write to a file. -c, --combine combine consecutive rules with the same matches but different targets. iptables does not currently support more than one target per match, so this simulates that by collecting the targets from consecutive iptables rules into one action tag, but only when the rule matches are identical. Terminating actions like RETURN, DROP, ACCEPT and QUEUE are not combined with subsequent targets. -v, --verbose Output xml comments containing the iptables line from which the XML is derived iptables-xml does a mechanistic conversion to a very expressive xml format; the only semantic considerations are for -g and -j targets in order to discriminate between <call> <goto> and <nane-of-target> as it helps xml processing scripts if they can tell the difference between a target like SNAT and another chain. Some sample output is: <iptables-rules> <table name="mangle"> <chain name="PREROUTING" policy="ACCEPT" packet-count="63436" byte-count="7137573"> <rule> <conditions> <match> <p>tcp</p> </match> <tcp> <sport>8443</sport> </tcp> </conditions> <actions> <call> <check_ip/> </call> <ACCEPT/> </actions> </rule> </chain> </table> </iptables-rules> Conversion from XML to iptables-save format may be done using the iptables.xslt script and xsltproc, or a custom program using libxsltproc or similar; in this fashion: xsltproc iptables.xslt my-iptables.xml | iptables-restore BUGS
None known as of iptables-1.3.7 release AUTHOR
Sam Liddicott <azez@ufomechanic.net> SEE ALSO
iptables-save(8), iptables-restore(8), iptables(8) iptables 1.4.21 IPTABLES-XML(1)
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