Threat Level: green Handler on Duty: Didier Stevens

SANS ISC: Scanning for Outlook Web Access (OWA) & Microsoft Exchange Control Panel (ECP) SANS ISC InfoSec Forums

Watch ISC TV. Great for NOCs, SOCs and Living Rooms: https://isctv.sans.edu

Sign Up for Free!   Forgot Password?
Log In or Sign Up for Free!
Scanning for Outlook Web Access (OWA) & Microsoft Exchange Control Panel (ECP)

This past two weeks my honeypot captured several probe for this URL /owa/auth/logon.aspx?url=https://1/ecp/ looking for the Exchange Control Panel. In the February 2020 patch Tuesday, Microsoft released a patch for ECP (CVE-2020-0688) for a remote code execution vulnerability affecting Microsoft Exchange server. Zero Day Initiative provided more details for this vulnerability here. Using CyberChef URL Decode, this is the output of the scan:

tcp-honeypot-20200502-072120.log:20200502-092115: 192.168.25.9:443-162.243.136.126:40998 data 'GET /owa/auth/logon.aspx?url=https://1/ecp/ HTTP/1.1\r\nHost: XX.YY.87.76\r\nUser-Agent: Mozilla/5.0 zgrab/0.x\r\nAccept: */*\r\nAccept-Encoding: gzip\r\n\r\n'

This is a sample of the logs received over the past two weeks. You will notice that all the inbound scans are all from the same IP range owned by the same ASN.

Sample of Scanning Activity
tcp-honeypot-20200502-072120.log:20200502-092115: 192.168.25.9:443-162.243.136.126:40998 data 'GET /owa/auth/logon.aspx?url=https%3a%2f%2f1%2fecp%2f HTTP/1.1\r\nHost: XX.YY.87.76\r\nUser-Agent: Mozilla/5.0 zgrab/0.x\r\nAccept: */*\r\nAccept-Encoding: gzip\r\n\r\n'
tcp-honeypot-20200507-140821.log:20200508-060105: 192.168.25.9:443-162.243.142.247:43656 data 'GET /owa/auth/logon.aspx?url=https%3a%2f%2f1%2fecp%2f HTTP/1.1\r\nHost: XX.YY.87.76\r\nUser-Agent: Mozilla/5.0 zgrab/0.x\r\nAccept: */*\r\nAccept-Encoding: gzip\r\n\r\n'
tcp-honeypot-20200515-181040.log:20200516-160625: 192.168.25.9:443-162.243.138.144:45092 data 'GET /owa/auth/logon.aspx?url=https%3a%2f%2f1%2fecp%2f HTTP/1.1\r\nHost: XX.YY.87.76\r\nUser-Agent: Mozilla/5.0 zgrab/0.x\r\nAccept: */*\r\nAccept-Encoding: gzip\r\n\r\n'

If your organization has made OWA available on the web, verify  the cumulative updates and the service pack that addressed this remote code execution vulnerability found in Microsoft Exchange 2010, 2013, 2016, and 2019 has been applied.

[1] https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0688
[2] https://www.zerodayinitiative.com/blog/2020/2/24/cve-2020-0688-remote-code-execution-on-microsoft-exchange-server-through-fixed-cryptographic-keys
[3] https://isc.sans.edu/ipinfo.html?ip=162.243.136.126

-----------
Guy Bruneau IPSS Inc.
My Handler Page
Twitter: GuyBruneau
gbruneau at isc dot sans dot edu

Guy

481 Posts
ISC Handler
May 16th 2020

Sign Up for Free or Log In to start participating in the conversation!