CertEagle – Asset monitoring utility using real time CT log feeds

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CertEagle 1 logo

In Bugbounties “If you are not first , then you are last” there is no such thing as silver or a bronze medal , Recon plays a very crucial part and if you can detect/Identify a newly added asset earlier than others then the chances of you Finding/Reporting a security flaw on that asset and getting rewarded for the same are higher than others.

Personally I am monitoring CT logs for domains/subdomains for quite a long time now and it gave me a lot of successful results , The inspiration behind this was “Sublert : By yassineaboukir” which checks crt.sh for subdomains and can be executed periodically , However I am using somewhat different approach and instead of looking into crt.sh periodically, I am extracting domains from Live CT log feeds , So chances of me finding a new asset earlier is higher as compared to others.

Detailed Description about this can be found here :

Read Blog here : https://medium.com/@Asm0d3us/weaponizing-live-ct-logs-for-automated-monitoring-of-assets-39c6973177c7


  • Monitoring Real Time CT log feed and extracting the domain names from that feed
  • Matching the extracted subdomains/domains against the domains/Keywords to be matched
  • Sending a Slack notification if a domain name matches

Requirements :

  • A VPS (UNIX up and running)
  • Python 3x (Tested with Python 3.6.9)
  • Slack Workspace (optional)


I am assuming that you have already done with your setup of slack workspace .

Now Create a channel named “subdomain-monitor” and set up a incoming webhook

Enabling Slack Notifications :

Edit config.yaml file and paste your slack webhook URL there , It should look something like this

CertEagle 2 config

Keywords and domains to match :

You can specify keywords and domains to match in domains.yaml file , You can specify names

For Matching subdomains :

CertEagle 3 domains

Note : Notice that preceding dot [ . ]

Lets take “.facebook.com” as example , domains extracted from Real time CT logs will be matched against the word “.facebook.com” , if matched they will be logged in our output file (found-domains.log) . The thing to note here is , It will give some false positives like “test.facebook.com.test.com” , “example.facebook.company” but we can filter out them later on by using use regex magic

For Matching domains/subdomains with specific keywords :

Lets assume that you want to monitor and log domains/subdomains that are having word “hackerone” in them , then our domains.yaml file will look something like this 

CertEagle 4 keyword

Now all the extracted domains/subdomains that are having word “hackerone” in them will be matched and logged (and a slack notification will be sent to you for the same)

Okay we are done with our initial setup , Lets install the required dependencies and run our tool

$ pip3 install -r requirements.txt

$ python3 certeagle.py

CertEagle 5 start

Matched domains will look like this :

CertEagle 6 output


Slack Notifications will look like this :

CertEagle 7 slack

Output files :

The program will keep on running all the matched domains will be saved under output directory in found-domains.log file

CertEagle 8 found domains

Strict Warning : Do not monitor assets of any organisation without prior consent



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Shoot my DM : @0xAsm0d3us

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