Securing a SA:MP Server Against Flood Attacks and Spoofed Packets in Pawn

The native SA:MP server networking engine is heavily reliant on an obsolete version of the RakNet library. The core structural vulnerability of this architecture is its implicit trust in client-side data dispatches. Exploitation software (malicious Lua scripts, custom rackbots, damage-changing tools, or network flooders) abuses this implicit trust pattern to execute internal game-protocol exploits. They spoof rapid vehicle creations, dispatch thousands of pickup collection packets per second, or spam authorization payloads, driving the server's TPS to zero and causing connection drops for legitimate players.

Standard Pawn callback triggers (such as OnPlayerPickUpPickup) execute only after the server engine has expended CPU cycles compiling the network packet layer. The only strategy to establish a defensive perimeter is to intercept and drop malicious network traffic early using the Pawn.RakNet plugin or a comprehensive protection layer like Nex-AC. In this article, we will examine how to build this proactive network defense.

Understanding the Network Layer: RPCs vs. Packets

Data transmission between the client application and the hosting instance inside SA:MP is split into two packet types:

• Packets: Low-level network synchronization arrays containing physics telemetry (player position vectors, heading angles, velocity metrics). These stream continuously dozens of times per second.
• RPC (Remote Procedure Call): High-level remote procedure executions. These tell the server about a definitive client action: text dispatches, keystrokes, entering an interior dimension, attempting to board a vehicle, or triggering a pickup event.

Anatomy of a Flood Exploit: A cheat module initiates a looping script that floods the server with RPC_PickedUpPickup (ID: 131) payloads at an aggressive rate of 5,000 dispatches per second. The server thread attempts to process each iteration, calling complex game mode verification routines. The hosting CPU spikes to 100% capacity, leaving the server unable to respond to regular network tasks.

Part 1: Low-Level Packet Filtering via Pawn.RakNet

The Pawn.RakNet plugin gives developers a native hook interface to intercept incoming RPC payloads before they exhaust the core game engine thread. We can drop the malicious packet and drop the socket connection immediately.

Preventing Pickup Flooding and Spoofed Vehicle Spawning:

Inject this protective architecture directly into your game mode script to track the frequency metrics of incoming high-load RPC paths per player slot:

#include <Pawn.RakNet>

#define RPC_PICKED_UP_PICKUP      131
#define RPC_VEHICLE_CREATE        22

static last_pickup_tick[MAX_PLAYERS];
static pickup_flood_count[MAX_PLAYERS];

public OnIncomingRPC(playerid, rpcid, BitStream:bs)
{
    if(rpcid == RPC_PICKED_UP_PICKUP)
    {
        new current_tick = GetTickCount();
        
        if(current_tick - last_pickup_tick[playerid] < 200)
        {
            pickup_flood_count[playerid]++;
            if(pickup_flood_count[playerid] > 5)
            {
                printf("[Security] Player ID %d kicked for pickup flooding.", playerid);
                Kick(playerid);
                return 0;
            }
        }
        else
        {
            pickup_flood_count[playerid] = 0;
        }
        last_pickup_tick[playerid] = current_tick;
    }

    if(rpcid == RPC_VEHICLE_CREATE)
    {
        if(GetPlayerAdminLevel(playerid) == 0)
        {
            printf("[Security] Blocked custom vehicle spawn exploit from client ID %d.", playerid);
            Kick(playerid);
            return 0;
        }
    }
    return 1;
}

Part 2: Securing Connection and Authorization Loops

Another common vector is botnet flooding (e.g., using RakDroid or generic RakBots), where 100–200 socket accounts flood the connection grid simultaneously. These automated sessions bypass the actual player spawning phase, hanging inside the authorization loop while spamming continuous login attempts or skin class changes (Class Requests) to saturate network bandwidth buffers.

Throttling Dialog Responses and Class Requests:

Utilize the low-level RPC interception wrapper to throttle the maximum transaction thresholds for unauthenticated player slots:

#define RPC_DIALOG_RESPONSE       62
#define RPC_REQUEST_CLASS         129

public OnIncomingRPC(playerid, rpcid, BitStream:bs)
{
    if(PlayerInfo[playerid][pIsLoggedIn] == false)
    {
        if(rpcid == RPC_DIALOG_RESPONSE)
        {
            static last_dialog_tick[MAX_PLAYERS];
            if(GetTickCount() - last_dialog_tick[playerid] < 150)
            {
                Kick(playerid);
                return 0;
            }
            last_dialog_tick[playerid] = GetTickCount();
        }

        if(rpcid == RPC_REQUEST_CLASS)
        {
            static class_requests[MAX_PLAYERS];
            class_requests[playerid]++;
            if(class_requests[playerid] > 10)
            {
                Kick(playerid);
                return 0;
            }
        }
    }
    return 1;
}

Part 3: Deploying Nex-AC (Integrated Anticheat Architecture)

If you prefer an out-of-the-box, comprehensive defensive layer instead of manually configuring individual RPC filters, implementing the proven Nex-AC framework is highly recommended. This module contains built-in network rate throttling designed to mitigate macro threats, including fake packet flags (NOP anomalies), CarShot exploits, FlyHacks, and connection floods.

1. Download the core nex-ac.inc file alongside the matching nex-ac.so runtime binary (for Linux environments).
2. Place the compiled nex-ac.so binary within your server's plugins/ folder and drop the nex-ac.inc include file inside your pawno/include/ compiler path.
3. Include the library header at the absolute top boundary of your game mode source file, directly following the baseline a_samp invocation:

   #include <a_samp>
   #include <nex-ac>

4. Open the dynamically compiled configuration file located at scriptfiles/nex-ac_settings.cfg following the initial launch cycle, and calibrate its internal metrics to match your hosting hardware throughput capabilities:

anti_flood_connect 5      # Maximum socket connections allowed per single IP per second
max_ping 500              # Drops latency exploits (Lag-Flooding profiles)
kick_on_flood 1           # Automatically drops connection socket upon packet rate violation
minify_object_bullet 1    # Optimizes handling matrices for bullet trace data (RapidFire prevention)

Summary: Protecting a SA:MP server requires proactive networking filters. Isolate and discard anomalous payloads at the low-level plugin boundary before they translate into executions inside your heavy game mode logic loops. This strategy guarantees a locked 50.0 TPS state even during intense malicious flood activities.