[Snort-sigs] Snort-sigs Digest, Vol 12, Issue 50

Y M snort at outlook.com
Fri Jun 8 11:17:03 EDT 2018


Thank you, Ashlee. That makes sense. Would the non-pcre version of the rules still fall within acceptable thresholds of performance vs. detection? Just in case non-obfuscated documents are encountered.

Thanks.
YM

_____________________________
From: Ashlee Benge <abenge at sourcefire.com>
Sent: Friday, June 8, 2018 5:22 PM
Subject: Re: [Snort-sigs] Snort-sigs Digest, Vol 12, Issue 50
To: snort-sigs at lists.snort.org <snort-sigs at lists.snort.org>


Yaser,

      We have reviewed the rules you submitted for CVE-2017-8570. Unfortunately, due to the obfuscation method used in the samples and a lack of static content matches,performance concerns prevent us from adding these rules to the ruleset.

On Tue, May 29, 2018 at 1:24 PM, <snort-sigs-request at lists.snort.org<mailto:snort-sigs-request at lists.snort.org>> wrote:
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Today's Topics:

   1. Win.Trojan.Dropper (O C)
   2. CVE-2017-8570 (O C)


----------------------------------------------------------------------

Message: 1
Date: Tue, 29 May 2018 17:23:40 +0000
From: O C <snort at outlook.com<mailto:snort at outlook.com>>
To: snort-sigs <snort-sigs at lists.snort.org<mailto:snort-sigs at lists.snort.org>>
Subject: [Snort-sigs] Win.Trojan.Dropper
Message-ID:
        <BN6PR1701MB18437AD38F6A61C998EECA4AA86D0 at BN6PR1701MB1843.namprd17.prod.outlook.com<mailto:BN6PR1701MB18437AD38F6A61C998EECA4AA86D0 at BN6PR1701MB1843.namprd17.prod.outlook.com>>

Content-Type: text/plain; charset="iso-8859-1"

Hi,

This downloader uses a rather unique User-Agent. Pcap is available for this one.

# --------------------
# Date: 2018-05-28
# Title: Win.Trojan.Dropper
# Tests: pcap
# Reference: https://www.virustotal.com/#/file/782cc4188618cf0c4815f85ea7873a004464095f5ed459b8d1579fa27ce5810e/detection

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"MALWARE-CNC known malicious user-agent - Win.Trojan.Dropper"; flow:to_server,established; content:"User-Agent: HTTPREAD|0D 0A|"; fast_pattern:only; metadata:ruleset community, service http; reference:url,www.virustotal.com/#/file/782cc4188618cf0c4815f85ea7873a004464095f5ed459b8d1579fa27ce5810e/detection<http://www.virustotal.com/#/file/782cc4188618cf0c4815f85ea7873a004464095f5ed459b8d1579fa27ce5810e/detection>; classtype:trojan-activity; sid:8000074; rev:1;)

Thanks.
YM
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Message: 2
Date: Tue, 29 May 2018 17:24:12 +0000
From: O C <snort at outlook.com<mailto:snort at outlook.com>>
To: snort-sigs <snort-sigs at lists.snort.org<mailto:snort-sigs at lists.snort.org>>
Subject: [Snort-sigs] CVE-2017-8570
Message-ID:
        <BN6PR1701MB184314ADF9539049956466D5A86D0 at BN6PR1701MB1843.namprd17.prod.outlook.com<mailto:BN6PR1701MB184314ADF9539049956466D5A86D0 at BN6PR1701MB1843.namprd17.prod.outlook.com>>

Content-Type: text/plain; charset="iso-8859-1"

Hi,

This one is similar to the existing signatures 45415 and 45416. The only difference is that is uses the StdOleLink Moniker as opposed to the Composite Moiker. There are 2 versions for each rule. The first one is without using PCRE. The samples I worked with had the moniker slightly manipulated, and PCRE was a perfect fit. Pcaps available for these.

Note that the sample documents contain multiple exploits and not just one.

# --------------------
# Date: 2018-05-06
# Title: CVE-2017-8570 StdOleLink
# Reference: https://www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection,https://www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection
# Tests: pcap

alert tcp $EXTERNAL_NET $FILE_DATA_PORTS -> $HOME_NET any (msg:"FILE-OFFICE RTF StdOleLink Moniker object creation attempt - NON-PCRE"; flow:to_client,established; flowbits:isset,file.rtf; file_data; content:"|5C|objupdate"; content:"003000000000000C000000000000046"; distance:0; fast_pattern; nocase; content:"C6AFABEC197FD211978E0000F8757E2A"; distance:0; nocase; metadata:ruleset community, service ftp-data, service http, service imap, service pop3; reference:cve,2017-8570; reference:url,portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570<http://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570>; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection<http://www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection>; reference:url,www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection<http://www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection>; classtype:attempted-user; sid:8000070; rev:1;)

alert tcp $EXTERNAL_NET $FILE_DATA_PORTS -> $HOME_NET any (msg:"FILE-OFFICE RTF StdOleLink Moniker object creation attempt - PCRE"; flow:to_client,established; flowbits:isset,file.rtf; file_data; content:"|5C|objupdate"; content:"003000000000000C000000000000046"; distance:0; fast_pattern; nocase; pcre:"/[ABCDEF0-9\x20\x0a\x0d0a]{32}/"; distance:0; nocase; metadata:ruleset community, service ftp-data, service http, service imap, service pop3; reference:cve,2017-8570; reference:url,portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570<http://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570>; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection<http://www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection>; reference:url,www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection<http://www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection>; classtype:attempted-user; sid:8000071; rev:1;)

alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"FILE-OFFICE RTF StdOleLink Moniker object creation attempt - NON-PCRE"; flow:to_server,established; flowbits:isset,file.rtf; file_data; content:"|5C|objupdate"; content:"003000000000000C000000000000046"; distance:0; fast_pattern; nocase; content:"C6AFABEC197FD211978E0000F8757E2A"; distance:0; nocase; metadata:ruleset community, service ftp-data, service http, service imap, service pop3; reference:cve,2017-8570; reference:url,portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570<http://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570>; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection<http://www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection>; reference:url,www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection<http://www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection>; classtype:attempted-user; sid:8000072; rev:1;)

alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"FILE-OFFICE RTF StdOleLink Moniker object creation attempt - PCRE"; flow:to_server,established; flowbits:isset,file.rtf; file_data; content:"|5C|objupdate"; content:"003000000000000C000000000000046"; distance:0; fast_pattern; nocase; pcre:"/[ABCDEF0-9\x20\x0a\x0d0a]{32}/"; distance:0; nocase; metadata:ruleset community, service ftp-data, service http, service imap, service pop3; reference:cve,2017-8570; reference:url,portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570<http://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8570>; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection<http://www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection>; reference:url,www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection<http://www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection>; classtype:attempted-user; sid:8000073; rev:1;)

Thanks.
YM

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End of Snort-sigs Digest, Vol 12, Issue 50
******************************************



--
Ashlee Benge
Detection Response Team
Talos Group


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