nanog mailing list archives
Re: Synful Knock questions...
From: Alain Hebert <ahebert () pubnix net>
Date: Tue, 15 Sep 2015 17:06:17 -0400
Well, It would be pointless to do, If the flash version and the running executable already replaced that function to return the right MD5 as from the CCO repository... But yes, scheduling the downloading the firmware and doing a SHA512 from your known good source (aka the Cisco one pre-deployement), would be the method I would use. ( We're doing it quarterly in some cases ) ----- Alain Hebert ahebert () pubnix net PubNIX Inc. 50 boul. St-Charles P.O. Box 26770 Beaconsfield, Quebec H9W 6G7 Tel: 514-990-5911 http://www.pubnix.net Fax: 514-990-9443 On 09/15/15 16:46, Stephen Satchell wrote:
On 09/15/2015 11:40 AM, Jake Mertel wrote:C) keep the image firmware file size the same, preventing easy detection of the compromise.Hmmm...time to automate the downloading and checksumming of the IOS images in my router. Hey, Expect, I'm looking at YOU. Wait a minute...doesn't Cisco have checksums in its file system? This might be even easier than I thought, no TFTP server required... http://www.cisco.com/web/about/security/intelligence/iosimage.html#10 Switch#dir *.bin (Capture the image name) Switch#verify /md5 my.installed.IOS.image.bin The output is a bunch of dots (for a switch) followed by an output line that ends "= xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" with the x's replaced with the MD5 hash. The command is on 2811 routers, too. Maybe far more devices, but I didn't want to take the time to check. You would need to capture the MD5 from a known good image, and watch for changes.
Current thread:
- Re: Synful Knock questions..., (continued)
- Re: Synful Knock questions... Ricky Beam (Sep 15)
- Re: Synful Knock questions... Jake Mertel (Sep 15)
- Re: Synful Knock questions... Michael Douglas (Sep 15)
- Re: Synful Knock questions... Jake Mertel (Sep 15)
- Re: Synful Knock questions... Valdis . Kletnieks (Sep 15)
- Re: Synful Knock questions... Jake Mertel (Sep 15)
- Re: Synful Knock questions... Michael Douglas (Sep 15)
- Re: Synful Knock questions... Jared Mauch (Sep 15)
- Re: Synful Knock questions... Marcin Cieslak (Sep 15)
- Re: Synful Knock questions... Stephen Satchell (Sep 15)
- Re: Synful Knock questions... Valdis . Kletnieks (Sep 15)
- Re: Synful Knock questions... Alain Hebert (Sep 15)
- Re: Synful Knock questions... Blake Hudson (Sep 15)
- Re: Synful Knock questions... Paul Ferguson (Sep 15)
- Re: Synful Knock questions... Roland Dobbins (Sep 15)
- Re: Synful Knock questions... Royce Williams (Sep 16)
- Re: Synful Knock questions... Stephen Fulton (Sep 16)
- Re: Synful Knock questions... Stephen Fulton (Sep 16)
- Re: Synful Knock questions... Jake Mertel (Sep 25)
- Message not available
- Re: Synful Knock questions... Hank Nussbacher (Sep 26)
- Re: Synful Knock questions... Blake Hudson (Sep 16)
- RE: Re: Synful Knock questions... Darden, Patrick (Sep 16)