To block a specific User-Agent, it can be implemented in Nginx, Apache, or code (such as PHP, Python). 1. In Nginx, judge $http_user_agent by if and return 403; 2. In Apache, use SetEnvIfNoCase and Deny to deny access; 3. judge User-Agent in the program and intercept the request. Common UAs that need to be blocked include python-requests, curl, empty UA, etc. Choosing the appropriate method can effectively reduce garbage traffic and security risks.
If you want to block certain User-Agents, the method is actually not complicated, it mainly depends on which environment you operate. The most common scenario is at the server level (such as Nginx, Apache) or through code control (such as PHP, Python). The following are some practical operations.
How to block User-Agent in Nginx
If you are using Nginx as a web server, you can add rules directly to the configuration file to block specific User-Agents.
if ($http_user_agent ~* (keyword|another keyword) ) {
return 403;
}For example, you want to block access using "curl" or "Slurp":
if ($http_user_agent ~* (curl|Slurp) ) {
return 403;
}-
~*means case insensitive match -
return 403is the status code that returns prohibited access - After modifying the configuration, remember to reload nginx configuration:
nginx -s reload
This method is suitable for unified management of traffic inlets, which is efficient and easy to maintain.
How to set up blocking User-Agent in Apache
If you are using Apache, you can implement similar functions through .htaccess file or virtual host configuration.
Use SetEnvIf and Deny combination:
SetEnvIfNoCase User-Agent "Keyword" bad_bot Deny from env=bad_bot
For example, blocking requests from User-Agent that contain "bot" or "crawl":
SetEnvIfNoCase User-Agent "bot|crawl" bad_bot Deny from env=bad_bot
-
SetEnvIfNoCasesets environment variables insensitively -
Deny from env=bad_botmeans that access is denied if this variable is set
It is also suitable for website-level protection, suitable for users who do not want to use program code.
Use code to judge and intercept (PHP/Python example)
In some cases, it may be inconvenient for you to modify the server configuration, and it can also be handled in the program at this time.
PHP example:
$user_agent = $_SERVER['HTTP_USER_AGENT'];
if (preg_match('/keyword/i', $user_agent)) {
header('HTTP/1.1 403 Forbidden');
exit('Forbidden');
}Python Flask example:
from flask import request, abort
@app.before_request
def block_user_agents():
ua = request.headers.get('User-Agent')
if 'keyword' in ua:
abort(403)- This method is more flexible and can be combined with functions such as logging, dynamic blacklisting, etc.
- The disadvantage is that every request has to go through the logic, and its performance is not as good as server-level interception.
Common User-Agent types to block
Sometimes you will encounter some "suspicious" User-Agents, such as:
-
python-requests -
Go-http-client -
curl -
PostmanRuntime - Empty User-Agent
These are often not normal requests made by the browser, but may be crawlers, test tools, or even attacks. Proper blocking of such UAs can reduce garbage flow and potential risks.
Basically these are the methods. Different environments have different solutions, just choose the most convenient one. The point is to identify the User-Agent string you want to block, and then select the appropriate location to block.
The above is the detailed content of How to block specific user agents?. For more information, please follow other related articles on the PHP Chinese website!
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