THC-SSL-DOS – DoS Tool Against Secure Web-Servers and for Testing SSL-Renegotiation

THC is The Hacker’s Choice. They are a group of hackers from Germany. Thc-SSL-dos is used for checking whether a website or server is enabled with SSL-renegotiation, thereby checking for renegotiation vulnerability (CVE-2009-3555).

SSL renegotiation is the process of renegotiating a client at the time of authentication. This tools sends SSL requests(Client Hello) to a webserver & then rejects the reply from the server(Server Hello) multiple times.

So eventually when the server tries to renegotiate during authentication, the client rejects it and thereby crashes the server making it a Denial of Service attack.

Also, this proves that the server is vulnerable to SSL-renegotiation vulnerability.



Syntax: thc-ssl-dos <options> ip port
-h -Help
-l <n> Limit parallel connections [default: 400]

Lab : Perform an SSL stress test on the router HTTPS login page

NOTE: This lab causes a DOS attack, it may temporary disable your target. Please use this tool wisely. Never use it on a company network without an agreement.

In this lab, we perform a dos attack on the https login page of the router web-based control panel. The SSL-dos sends requests to the SSL/HTTPS server.

When receiving acknowledgments, it rejects before handshake occurs. Thus the server tries again & again if SSL-renegotiation is enabled. Here the router ip is and HTTPS login page is running on port 443

Command: thc-ssl-dos 443 –accept
Starting THC-SSL-DOS
Verbose Operation

Now try to login to the page <replace with yours>

Router Login being denied


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