How can a high volume of requests potentially lead to a Denial of Service (DoS) attack on a server running PHP scripts?

A high volume of requests can overwhelm a server running PHP scripts, causing it to become unresponsive or crash, leading to a Denial of Service (DoS) attack. To mitigate this issue, we can implement rate limiting in our PHP scripts to restrict the number of requests that can be made within a certain time frame. 

// Implementing rate limiting to prevent DoS attacks
$limit = 100; // Maximum number of requests allowed
$timespan = 60; // Time frame in seconds
$ip = $_SERVER['REMOTE_ADDR']; // Get the client's IP address

// Connect to database to store request details
$pdo = new PDO('mysql:host=localhost;dbname=rate_limiting', 'username', 'password');

// Check if the IP has exceeded the limit within the specified time frame
$stmt = $pdo->prepare("SELECT COUNT(*) FROM requests WHERE ip = :ip AND timestamp >= NOW() - INTERVAL :timespan SECOND");
$stmt->bindValue(':ip', $ip);
$stmt->bindValue(':timespan', $timespan);
$stmt->execute();
$count = $stmt->fetchColumn();

if ($count < $limit) {
    // Process the request
    // Insert the request details into the database
    $stmt = $pdo->prepare("INSERT INTO requests (ip, timestamp) VALUES (:ip, NOW())");
    $stmt->bindValue(':ip', $ip);
    $stmt->execute();
} else {
    // Return an error message or redirect to a different page
    echo "Rate limit exceeded. Please try again later.";
}

Keywords

PHP server Denial of Service high volume requests

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