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; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection; reference:url,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; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection; reference:url,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; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection; reference:url,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; reference:url,www.virustotal.com/#/file/bebd4cd9aece49fbe6e7024e239638004358ff87d02f9bd4328993409da9e17c/detection; reference:url,www.virustotal.com/#/file/af9ed7de1d9d9d38ee12ea2d3c62ab01a79c6f4b241c02110bac8a53ea9798b5/detection; classtype:attempted-user; sid:8000073; rev:1;)


Thanks.
YM