How to protect your SMS API from Bot Attack!

Do you ever wonder how safe APIs are? And are they really safe from the world of cyber threats? 

As with everything on the World Wide Web, APIs are not immune to external threats, and thus measures have to be taken to mitigate these issues effectively. The various forms of threats can range from MITM and API injections like XSS & SQLi, to DDoS attacks. A fact that also has to be considered is that each attack has its distinct nature. 

Bots have evolved with the internet as well, and they can create a lot of nuisance from hacking to even denying data access to credible users.

APIs need to implement a different approach to stay safe and a step ahead of these bots. Some of these are discussed as follows:

Geo- Protection

Restrictions that block access of entire countries will provide the service providers with the liberty to choose the geographical extent of the target, making it more effective and less susceptible to bots from various sources. It further empowers with the choice of providing or denying access based on numerous criteria like Country code or referrer domain.

Block the outdated user agents/browsers

It is not widely influential, although some contingency can be achieved. Most of the current browsers have implemented a step to stay inactive unless the user updates the software. This is to curb the risks from the string lists attached with the default configurations in outdated agents.

Block the known threats

Known proxy sites could be the threat you might not have seen coming. Assuming that the bots are implementing higher technology can be an ignorant move. Denying access to these known proxy sites might not be very impactful but will surely discourage bots from coming after you through these portals.

We identify and block the known proxy sites and even enable you to report any when identified.

Securing the IP

Sending messages to a fishy IP address can prove disastrous. So ensure that your service-related and transactional SMSs are sent only to 'whitelisted' IPs. This distinction is necessary since bots can appear with seemingly ordinary IPs.

We provide this additional security feature, and with our API security enabled, if you attempt to reach a questionable IP, an error code of 418 will reject the attempts.

Integration using Token in OTP Widget will help to prevent Bot attack

For instructions, please refer to this guide:

Identify repetitive attempts 

Using a Re-captcha can be one of the best means to discourage bots, and it is not just a free service but also relatively simple for your usual human user. It might be even fun to some, like a puzzle. Once the login process has been secured, attention might be paid to the number of attempts, especially from the same IP.

You can choose after how many failed attempts from a similar IP, IP get blocked. 


With a lead and expertise in the transactional SMS biz, MSG91 has stood out to you, owing to its many great features, and security concerns are just one of them. Bots can be annoying, especially when you're trying to put your best step forward, and we ensure that you do so in the most secure way possible.