Hey there! Want to learn how to check SMS API rate limits with Python? You’re in the right spot! Rate limits are super important—they control how many requests an API can handle at once, keeping things fair and preventing misuse. I’ve worked as an ethical hacker to help clients secure their SMS APIs, and I’m thrilled to share my experience with you. We’ll use Burp Suite to grab API requests and Python to automate the testing process, all while keeping things ethical and responsible. Let’s jump into this step-by-step guide to help make APIs more secure!
Table of Contents
What Are SMS API Rate Limits?
SMS APIs, the kind that send OTPs for logging in or verifying accounts, usually have rate limits to manage how many requests you can make in a set time—like 10 requests per minute. These limits are there to prevent misuse, like someone flooding a phone number with OTP messages. But if the limits are too loose, they can leave the API open to trouble. I’ve seen APIs that let you send hundreds of requests without stopping you, which can cause server issues or even cost the company a lot of money. Checking these limits helps make sure they’re doing their job.
Why Should You Check Rate Limits?
Looking into SMS API rate limits is a big part of ethical hacking. Here’s why it matters:
- Find Weak Spots: If the limit is too high, someone could exploit it.
- Boost Security: You can suggest better limits to developers to stop misuse.
- Learn How APIs Work: See how the API reacts when you send a bunch of requests.
I once worked with a client whose SMS API let you send 50 OTPs in a minute—no cap! That’s a problem. After some testing, we brought it down to 5 per minute, which made their system way safer. Let’s go through how you can do this yourself.
Another Option: Using Burp Suite Intruder
Now, you could also check SMS API rate limits using Burp Suite’s Intruder tool—it’s great for sending a bunch of requests fast and seeing when the API blocks you. I’ve used Intruder before to hammer an API with requests and watch for a 429 status code, which means “too many requests.” But in this guide, I’m sticking with Python because it gives you more flexibility to build and customize your own tools. For example, you could tweak the script to create something like an SMS bomber for testing (ethically, of course!), or even add features to monitor other API behaviors. Python lets you grow your skills and develop more advanced security tools down the road.
Grabbing SMS API Requests with Burp Suite
First, we need to see how the SMS API works by capturing a request. I love using Burp Suite for this—it’s a great tool for snooping on web traffic. Here’s how I set it up:
- Get Burp Suite: Download it from their official website and open it up. If you’re new, the free Community Edition works fine.
- Set Up the Proxy: Tell your browser to send its traffic through Burp’s proxy, which is usually at 127.0.0.1:8080. You’ll also need to install Burp’s CA certificate to deal with HTTPS requests.
- Make a Request: Go to a site that sends OTPs, type in your phone number, and request an OTP. Burp will catch the request for you.
A Little Advice: Always test on a site you’re allowed to mess with. I usually set up my own test site so I don’t accidentally cause trouble.
Breaking Down the SMS API Request
Once you’ve got the request in Burp’s Proxy > Intercept tab, let’s take a closer look at it. Here’s what I check for:
- URL: The API endpoint, something like /api/bloger/cta/push-data.
- Method: It’s usually a POST request for sending SMS.
- Headers: Stuff like Content-Type (often application/x-www-form-urlencoded) and User-Agent.
- Payload: The data being sent, like mobile (your phone number) and user_action (like send_otp).
When I looked at one API, I noticed it didn’t send back any rate limit info in the headers—like X-RateLimit-Limit. That’s a sign we’ll need to test it ourselves to see how many requests it lets through before it says “no more.”
Setting Up a Python Script to Test Rate Limits
Now let’s use Python to recreate that SMS API request. We’ll use the requests library to send the request and start testing. First, we’ll set up the headers and payload from what we saw in Burp.
Headers
Here’s how I turned the headers into a Python dictionary:
headers = {
"Host": "services.example.com",
"Sec-Ch-Ua": '"Chromium";v="119", "Not?A_Brand";v="24"',
"Accept": "*/*",
"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
"Sec-Ch-Ua-Mobile": "?0",
#add all headers
}Payload
Next, the payload with my phone number and the action:
payload = {
"source_page": "-",
"event_to": "MoEngage",
"ui_name": "GetStarted",
"cta_name": "cta_GetStart",
"cta_type": "Sign Up CTA",
"cta_route": "https://services.example.com/api/bloger/cta/push-data",
"user_action": "send_otp",
"record_id": "0",
"name": "jam",
"mobile": "9999555545",
#add all parameters
}Sending One Request
Here’s a quick script to send a single request and see if it works:
import requests
url = "https://services.example.com/api/bloger/cta/push-data"
response = requests.post(url, headers=headers, data=payload)
print(f"Status Code: {response.status_code}")I always start with one request to make sure everything’s working. It’s a good way to double-check that I copied the headers and payload correctly.
Adding Logic to Detect Rate Limits
To figure out the SMS API rate limits, we need to send a bunch of requests and see when the API stops us. I’ll add a loop to send multiple requests, plus some code to spot when we hit the limit. We’ll also let the user pick the phone number and how many requests to send:
import requests
import time
def send_sms_request(target_number):
url = "https://services.example.com/api/bloger/cta/push-data"
headers = {
#all headers
}
payload = {
#all payload parameters
}
response = requests.post(url, headers=headers, data=payload)
return response
target_number = input("Enter the phone number to test (make sure you have permission): ")
num_requests = int(input("How many requests do you want to send? "))
for i in range(num_requests):
print(f"Sending request number {i+1}...")
response = send_sms_request(target_number)
print(f"Status Code: {response.status_code}")
if response.status_code == 429: # This code means "Too Many Requests"
print("Whoa, we hit the rate limit! The API stopped us.")
break
time.sleep(1) # Wait a second between requests so we don’t overload the serverThe 429 status code usually means you’ve hit the rate limit, but some APIs might handle it differently. If you don’t see 429, check the response message for clues.
Keeping Things Private with Proxies
When I’m testing rate limits, I like to keep my identity private using the Tor network. It hides my IP address and helps me see how the API might respond to anonymous traffic, which is something attackers might try. Here’s how I set it up:
- Start Tor: On my system, I run sudo service tor start. Tor listens on 127.0.0.1:9050 for SOCKS5 connections.
- Add Proxies to the Script: I tweak the request to go through Tor:
proxies = {
"http": "socks5://127.0.0.1:9050",
"https": "socks5://127.0.0.1:9050"
}
response = requests.post(url, headers=headers, data=payload, proxies=proxies)Full Python Script for Rate Limit Testing
Lessons Learned About SMS API Security
Digging into SMS API rate limits with Python has taught me a ton about keeping APIs safe. Here’s what I’ve learned:
- Rate Limits Are Key: If they’re too loose, someone could spam OTPs or overload the server.
- Python Makes It Easy: Using Python to test limits is straightforward and lets you be thorough.
- Stay Ethical: Always get permission, test in a safe environment, and don’t stress the server too much.
I hope this guide helps you check SMS API rate limits and make APIs more secure. Have you ever tested an API like this? Drop a comment below—I’d love to hear your stories!