Skip to main content

Fun with Firewall Logs

So, after my post about ask.com's network...  Here's another quiz for you.

Feb 15 09:16:39 localhost kernel: IN=eth0 OUT= MAC=00:03:47:f1:52:0d:00:18:01:b6:c1:4d:08:00 SRC=121.242.15.135 DST=192.168.x.x LEN=72 TOS=0x00 PR

EC=0x00 TTL=45 ID=32394 DF PROTO=TCP SPT=52764 DPT=22 WINDOW=46 RES=0x00 ACK PSH FIN URGP=0

What kind of fun is that!

Comments

Jeremy Johnson said…
Ok...it's been a while, but it looks like a Linux box in India is trying to hit your box using SSH...am I close?
Joel said…
Correct, that's part of it. But not the most interesting part.
Scott said…
Lol. I like the flag combo. ack psh fin urg. It's got a nice rhythm to it. Could almost be a Salt n Peppa song.
Joel said…
No urg flag. But otherwise correct.
Jeremy Johnson said…
Ok...it's been a while, but it looks like a Linux box in India is trying to hit your box using SSH...am I close?
Joel said…
Correct, that's part of it. But not the most interesting part.
Scott said…
Lol. I like the flag combo. ack psh fin urg. It's got a nice rhythm to it. Could almost be a Salt n Peppa song.
Joel said…
No urg flag. But otherwise correct.
Basil said…
Your SSH service (running in a box with an Intel card) received a TCP session-close packet (FIN) from the client, through your Actiontec DSL modem that, I guess, can serve as a gateway for certain services.

I'm right? ;-)
Joel said…
Close. You were right on the actiontec part.
Basil said…
Your SSH service (running in a box with an Intel card) received a TCP session-close packet (FIN) from the client, through your Actiontec DSL modem that, I guess, can serve as a gateway for certain services.

I'm right? ;-)
Joel said…
Close. You were right on the actiontec part.
Joel said…
Close. You were right on the actiontec part.
james said…
Why is the dst a private IP and how did that packet get routed to you?
Joel said…
Because the DST is a private IP behind my firewall.
james said…
Why is the dst a private IP and how did that packet get routed to you?
Joel said…
Because the DST is a private IP behind my firewall.
Joel said…
Because the DST is a private IP behind my firewall.
Leon said…
I would think a couple of things could be happening here.

1) State table confusion in relation to actual connections
2) Port scan in progress using an uncommon flag config.

Oh thank the world for *STATEFUL* firewalls. :-)

Without supporting information I'm left with assumption and guesswork, take a look at snort.org :)
Leon said…
I would think a couple of things could be happening here.

1) State table confusion in relation to actual connections
2) Port scan in progress using an uncommon flag config.

Oh thank the world for *STATEFUL* firewalls. :-)

Without supporting information I'm left with assumption and guesswork, take a look at snort.org :)

Popular posts from this blog

Offset, Depth, Distance, and Within

Without going off the deep-end here and discussing every single Snort rule keyword, I just wanted to touch on a few modifiers that people sometimes misunderstand.  They aren't difficult, and hopefully after this explanation and a few examples, I can clear some of the air around these five modifiers.

The five modifiers that I am talking about are
OffsetDepthDistanceWithinnocaseThese five modifiers are not keywords of themselves, but rather they apply as modifiers to another keyword.  That keyword is "content". The content keyword is one of the easiest pieces of the Snort rules language as all it does is look for a particular string.  So for instance if I wanted to look for the word "joel" within a packet.  A simple:
content:"joel";Would allow me to do that.  The interesting part comes into play when you want to specify where inside of a particular packet you want the string "joel" to be looked for.  If you are running just a plain content ma…

Writing Snort Rules Correctly

Let me start off by saying I'm not bashing the writer of this article, and I'm trying not to be super critical.  I don't want to discourage this person from writing articles about Snort rules.  It's great when people in the Snort community step up and explain some simple things out there.  There are mistakes, it comes with the territory.  If you choose to be one of the people that tries to write Snort rules, you also choose to be someone who wants to learn how to do it better.  That's why I write this blog post, not to bash the writer, but to teach.

I noticed this post today over at the "Tao of Signature Writing" blog, and to be honest I glanced over most of it figuring it was a rehash of things I've already read or things that have already been written from countless people about "Here's how you write Snort rules!".  I scrolled down quickly skimming, not reading at all really, and noticed this part:
Now, let us look at the second questio…

Safari 5.1.4 now available

Safari 5.1.4 now available, fixes issues and improves performance | TUAW - The Unofficial Apple Weblog:


Improve JavaScript performanceImprove responsiveness when typing into the search field after changing network configurations or with an intermittent network connectionAddress an issue that could cause webpages to flash white when switching between Safari windowsAddress issues that prevented printing U.S. Postal Service shipping labels and embedded PDFsPreserve links in PDFs saved from webpagesFix an issue that could make Flash content appear incomplete after using gesture zoomingFix an issue that could cause the screen to dim while watching HTML5 videoImprove stability, compatibility and startup time when using extensionsAllow cookies set during regular browsing to be available after using Private BrowsingFix an issue that could cause some data to be left behind after pressing the "Remove All Website Data" button