Arp Spoofing in Nestjs with Dynamodb

Arp spoofing is a Layer 2 attack where an attacker sends falsified ARP messages to associate their MAC address with a legitimate IP, typically the default gateway or another service. In a NestJS application that uses DynamoDB, the risk is not that NestJS or the AWS SDK introduces an ARP spoofing flaw, but that the runtime environment and service dependencies can be targeted. When the app runs on EC2, ECS, or on-prem hosts, a compromised host on the same network can perform ARP spoofing to intercept traffic between the NestJS process and DynamoDB endpoints. Because DynamoDB connections rely on HTTPS/TLS, the encryption protects data in transit; however, an attacker who successfully redirects traffic via ARP spoofing can still observe session behavior, trigger requests, or attempt SSL stripping if misconfigurations exist (e.g., mixed content or HTTP fallbacks).

The NestJS layer can inadvertently expose a larger attack surface when logs, error messages, or debug endpoints reveal internal hostnames or IPs that aid an attacker in crafting ARP spoofing campaigns. For example, if the app exposes AWS region or endpoint metadata in responses or error traces, an attacker gains information about the DynamoDB service endpoint being used. Additionally, if the NestJS app is deployed in a containerized environment with shared network segments or if security groups and network ACLs are permissive, lateral movement becomes easier post-ARP cache poisoning. Unauthenticated SSRF or open proxy configurations in NestJS could compound this by allowing an attacker to route traffic through the app, increasing exposure to interception.

Importantly, the API security scanner checks such as BOLA/IDOR, Data Exposure, and SSRF—run as part of the 12 parallel security checks—can detect weak configurations that facilitate successful interception or session hijacking after an ARP spoofing foothold. While DynamoDB itself is a managed service with strong isolation, the surrounding infrastructure and application design determine whether an attacker can leverage ARP spoofing to affect the NestJS-DynamoDB interaction. Therefore, securing the host network, tightening container networking, and ensuring the NestJS app does not leak internal topology are essential mitigations.

Remediation focuses on network hardening, secure coding practices in NestJS, and safe DynamoDB integration. Ensure the NestJS app runs in a private subnet with controlled security group egress to DynamoDB only. Avoid exposing AWS metadata endpoints to the application. Use VPC endpoints for DynamoDB to keep traffic within the AWS network and reduce exposure to external ARP manipulation.

In code, always use the AWS SDK for JavaScript v3 with DynamoDB DocumentClient, and enforce TLS by ensuring the SDK is configured with httpsAgent and no custom httpAgent that disables certificate validation. Do not disable SSL verification or use HTTP. Below is a secure NestJS DynamoDB setup using the v3 SDK with explicit TLS and retry configuration:

import { DynamoDBDocumentClient, ScanCommand, PutCommand } from "@aws-sdk/lib-dynamodb"; import { DynamoDBClient } from "@aws-sdk/client-dynamodb"; import { HttpHandlerOptions } from "@aws-sdk/types";  const client = new DynamoDBClient({  region: process.env.AWS_REGION,  credentials: {   accessKeyId: process.env.AWS_ACCESS_KEY_ID!,   secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY!,  },  httpsAgent: new (require("https")).Agent({ keepAlive: true }),  // Explicitly enforce TLS; do not provide an httpAgent  maxAttempts: 3,  requestHandler: {    // Avoid custom handlers that might bypass TLS  } });  export const dynamoDb = DynamoDBDocumentClient.from(client);  // Example safe usage in a service class  export class ItemsService {  async scanItems() {   const command = new ScanCommand({ TableName: process.env.DYNAMODB_TABLE! });   const result = await dynamoDb.send(command);   return result.Items;  }   async createItem(data: any) {   const command = new PutCommand({    TableName: process.env.DYNAMODB_TABLE!,    Item: data,   });   return dynamoDb.send(command);  } }

Additionally, sanitize all inputs before they are passed to DynamoDB to prevent injection and ensure that error handling does not leak internal host or network details that could aid an attacker in mapping the environment for ARP spoofing. Rotate credentials via IAM roles where possible, and avoid long-lived access keys in the NestJS environment. Use middleware to strip sensitive information from logs and responses. Combine these practices with runtime scans using middleBrick to detect exposed debug endpoints or misconfigured CORS that could amplify network-based attacks.