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

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