Measuring quality

SIP DoS/DDoS Simulation

Nowadays as the Internet technologies have overwhelming success over traditional ones, they are still vulnerable since they constantly undergo numerous severe attacks. Undoubtedly one of the most popular fields in the sphere of internet technology is IP-telephony as it covers a wide demand among individuals and businesses.

SIP is generally accepted protocol for Voice over IP (VoIP) calls. A great number of VoIP service providers are available for public internet which means that they can become targets of denial of service (DoS) attacks and excessive calling (TDoS). In case you are an individual IP telephony user, this problem might not interest you to a great extent. However if your business operates mostly via call centers and cloud IP PBX software, or if you provide VoIP services, this can be crucial problem. DoS attacks can block incoming and outgoing calls i.e. which will result in breaking SLA agreements, loss of sales, contacts and eventually reputation. The DoS attack can be initiated by multiple sources (servers, IP addresses), in such case it is called distributed denial of service (DDoS) attack.

We published a public warning about DDoS and IP spoofing, please take a look.

You can prevent SIP DoS/DDoS attacks by configuring your software or by passing VoIP traffic via Session Border Controller (SBC) which is able to block SIP DoS attacks; also you can use VPN connections. Obviously it is better to stay on a safe side and know if you are capable of protecting your business from attacks before you experience a real attack. Our SIP Tester software tool is meant to simulate Layer 7 SIP DoS attack and test reliability of your VoIP infrastructure. It can generate up to 8000 simultaneous calls with RTP media per 1 server and 1000 calls per second, and you can run it on multiple servers, so you can measure maximum number of calls your server can process. Calls (INVITE messages) are generated with randomly with exponential probability distribution. Various complex scenarios of tests can be defined using CallXML script. The SIP Tester measures quality of the generated VoIP calls and reports
  • Percentage of answered calls
  • Average delay before answering
  • RTP jitter statistics
so you can measure quality of normal calls while your system is under DoS attack.
Since the basic license of our SIP Tester does not allow such things as IP spoofing, SIP scanning, SIP fuzzing, brute force attacks, etc., for advanced tests you can use our VoIP Security Test and Validation Suite and complex CallXML scripts. Here are few example tests tha you can perform:
  • Rent a IP spoofing-friendly (unfiltered) server, install SIP Tester with licensed VoIP security features
  • Run a simple script with sendspoofedudppacket: send INVITE, REGISTER or OPTIONS packets and spoofing source IP address, Via and Contact SIP headers. You should be able to send up to 50.000 packets per second
  • If you know that target server has IP whitelist, you can limit range of IP addresses for the spoofing, down to subnet(s)
  • Since source IP addresses are spoofed, the SIP packets should pass SBC's dynamic filters
  • Another test to run: modify default CallXML script and insert addsipmalformer elements, to see if your SBC crashes with fuzzed SIP packets. The "addsipmalformer" enables stateful SIP fuzzing; also it enables SIP flooding (e.g. excessive retransmission of SIP ACK packets)
  • One more test to run: RTP flooding and fuzzing with setrtpmalformer CallXML element. It randomly modifies bits in transmitted RTP packets (within normal SIP call) and optionally retransmits RTP packets many times, so it should be able to crash your media server
  • Contact us if you want us to run the DoS/DDoS tests from our side. We have a way to flood your network with UDP packets from 10.000 IP addresses


  • IP spoofing is possible only in LAN, unless ISP routers are compromised - true, but the fact is that we can not control all employees of all ISP's. And hackers can rent a server with IP spoofing, monthly price is less than 160USD (2019). We have managed to contact someone who sells spoofed servers via skype:
    IP-spoofed server hosting
    see more details
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