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Introduction
Rich Communication Services (RCS) was designed to replace SMS with encrypted, media‑rich conversations, but its business messaging APIs have become a spam superhighway. Under India’s IT (Intermediary Guidelines and Digital Media Ethics Code) Rules, 2021 (as amended in 2026), platforms like Google are legally required to address user grievances within 7 calendar days – a deadline that is currently being tested by a formal complaint about unchecked RCS spam originating from partners such as Jio Business Messaging. This article extracts technical vectors of RCS abuse, provides command‑line analysis tools across Linux and Windows, and builds a step‑by‑step framework for both offensive testing and defensive mitigation.
Learning Objectives
- Understand RCS protocol vulnerabilities (SIP, MSRP, HTTP/2) that enable spam injection and sender spoofing.
- Capture and dissect live RCS traffic using open‑source tools on Linux and Windows.
- Implement automated grievance reporting, cloud hardening, and ML‑based spam filtering against RCS abuse.
You Should Know
1. Deconstructing RCS Spam: Protocol Analysis and Capture
RCS uses SIP (port 5060) for session setup and MSRP (port 2855) for message transfer. Spammers often inject messages via misconfigured Business Messaging APIs or compromised RCS Application Servers. To see what’s hitting your Android device, capture live traffic.
Step‑by‑step (Linux/macOS):
- Identify your active network interface: `ip a` or
ifconfig. - Start a packet capture on ports commonly used by RCS:
sudo tcpdump -i wlan0 -s 0 -w rcs_spam_traffic.pcap 'port 5060 or port 2855 or port 2948'
- Generate traffic by sending an RCS message (or receiving spam). Stop with
Ctrl+C.
4. Analyse with Wireshark filters:
– `msrp` – show all MSRP packets, inspect `Message-ID` and Content-Type.
– `sip.Method == “MESSAGE”` – isolate SIP instant messages.
Windows alternative: Use Npcap with Wireshark. Capture with:
& 'C:\Program Files\Wireshark\tshark.exe' -i Ethernet -f "port 5060 or port 2855" -w rcs_spam.pcap
Look for malformed `To` headers or repetitive payloads – classic spam indicators.
- Automated Grievance Reporting: Python Script Against Google’s Portal
When manual reporting fails, script the complaint process. The IT Rules require Google India’s Resident Grievance Officer to acknowledge within 24 hours and reply “on the merits” within 7 days. Use a Python script to submit and follow‑up.
Step‑by‑step:
- Install required libraries: `pip install requests beautifulsoup4 captcha-solver` (use 2captcha API key for reCAPTCHA).
2. Create a script `grievance_bot.py`:
import requests, time
url = "https://support.google.com/legal/grievance"
payload = {
"name": "Your Name",
"email": "[email protected]",
"grievance_type": "RCS spam",
"description": "Jio Business Messaging bypassing consent...",
"platform": "Google Messages"
}
Automate CAPTCHA solve and submit
response = requests.post(url, data=payload)
print(response.status_code, "Complaint lodged")
3. Schedule daily checks for reply using `cron` (Linux):
crontab -e Add: 0 9 /usr/bin/python3 /home/user/check_grievance_status.py
4. The script can parse the portal’s status page via CSS selectors and send an email alert if Google misses the 7‑day deadline.
- Windows PowerShell: Live RCS Log Analysis from Android ADB
For users who don’t control the network, extract RCS logs directly from an Android device (debugging must be enabled).
Step‑by‑step:
- Install ADB and enable USB debugging on your Android.
2. In PowerShell (Admin):
adb logcat -b main -b system | Select-String -Pattern "RcsMessaging|RcsProvider|SpamFilter"
3. Filter for spam‑related events:
adb logcat -d | findstr /i "blocked pattern signature"
4. To monitor real‑time outbound connections from the Messages app:
Get-NetTCPConnection -State Established | Where-Object {$_.OwningProcess -eq (Get-Process -Name "com.google.android.apps.messaging").Id}
This reveals which IPs receive your message metadata – useful for spotting unauthorised exfiltration.
4. Cloud Hardening: Securing Business Messaging Gateways (AWS/Azure)
If you operate an RCS Business Messaging (RBM) agent, prevent becoming a spam source. Hardening focuses on API rate limiting and sender verification.
Step‑by‑step (AWS):
- Restrict API keys to specific IPs and services using IAM policies:
{ "Effect": "Deny", "Action": "rbm:messages.send", "Condition": {"NotIpAddress": {"aws:SourceIp": "203.0.113.0/24"}} } - Deploy AWS WAF on your API Gateway with a rate‑based rule:
– 500 requests per 5 minutes per IP → block.
– Add regex pattern to reject messages with multiple “click here” templates.
3. Use VPC endpoints for third‑party aggregators (e.g., Twilio, MessageBird) so traffic never traverses the public internet.
resource "aws_vpc_endpoint" "rbm_api" {
service_name = "com.amazonaws.us-east-1.execute-api"
vpc_id = aws_vpc.main.id
}
4. Enable CloudTrail logs for all RBM API calls and set up a Lambda that auto‑revokes keys if spam patterns (e.g., identical message bursts) exceed a threshold.
5. Vulnerability Exploitation: RCS Sender Spoofing (Educational)
Understanding how attackers forge sender IDs helps you build better filters. Many RCS providers omit proper authentication of the `X-Message-Domain` header.
Step‑by‑step (Kali Linux):
- Use `curl` to emulate an RCS Business Messaging API (simplified example):
curl -X POST https://rcs-gateway.example.com/v1/send \ -H "Authorization: Bearer [bash]" \ -d '{"from":"BankOfAmerica","to":"+919876543210","text":"Urgent: Your account will be suspended, click http://evil.com"}' - If the gateway does not validate `from` against a registered brand, spoofing succeeds.
- To test mitigation, deploy a local RCS sandbox using Google’s RCS Business Messaging test environment.
- On Linux, capture the attack and create a Suricata rule to block unauthenticated sender IDs:
alert tcp any any -> any 2855 (msg:"RCS Spoof Attempt"; content:"|22|from|22 3a 22|BankOfAmerica"; nocase; sid:1000001;)
Run Suricata on your network edge to drop such packets.
6. Mitigation: ML‑Based Spam Filtering for RCS
Because spam signatures evolve, train a lightweight classifier on message content and metadata.
Step‑by‑step:
- Export a dataset of RCS messages (use ADB logs from Section 3) labelled as spam/legit.
2. Python script using scikit‑learn:
from sklearn.feature_extraction.text import TfidfVectorizer from sklearn.naive_bayes import MultinomialNB import joblib msgs = ["Congratulations! You won a prize...", "Your appointment at 10am..."] labels = [1, 0] 1=spam vectorizer = TfidfVectorizer() X = vectorizer.fit_transform(msgs) model = MultinomialNB().fit(X, labels) joblib.dump((model, vectorizer), 'rcs_spam_model.pkl')
3. Integrate with Google Messages by using the Android Notification Listener API to intercept incoming RCS pushes, run inference, and auto‑delete spam.
4. For enterprise RCS gateways, wrap the send endpoint with a model check: reject messages with spam probability > 0.85.
7. Legal & Compliance Automation: Tracking Grievance Deadlines
To hold Google accountable, automate the tracking of each complaint. Use Linux cron and a status‑check API.
Step‑by‑step:
- After submitting a grievance, extract the unique ticket ID from the acknowledgement email (use IMAP).
- Bash script that polls the Google grievance status page for that ID:
!/bin/bash TICKET_ID="IND-2026-12345" STATUS=$(curl -s "https://support.google.com/legal/grievance/status?id=$TICKET_ID" | jq -r '.status') if [ "$STATUS" != "Resolved" ] && [ $(date -d "7 days ago" +%s) -gt $(date -d "$SUBMISSION_DATE" +%s) ]; then echo "Google missed the 7-day deadline!" | mail -s "RCS Spam Violation" [email protected] fi
- Use `slack-cli` to push alerts to a google-compliance channel.
- Maintain a database of deadlines; if Google fails repeatedly, automatically draft a follow‑up notice under IT Rule 4(2).
What Undercode Say
- Technical transparency is no substitute for legal teeth: Even with packet captures and ML filters, RCS spam persists because platforms monetise business messaging. The 7‑day grievance deadline is the only real pressure point.
- Automation shifts the balance: Scripting complaint submission, log analysis, and deadline tracking turns a one‑person fight into a scalable audit mechanism. Every researcher should adopt the PowerShell and Python tools above to force platform accountability.
- RCS protocol lacks native anti‑spoofing: Without mandatory TLS mutual authentication and senderID validation at the carrier level, spam will continue to evade traditional SMS blockers. The future requires IT Rules to mandate strict API security audits for all RCS partners.
Prediction
Within 18 months, the Indian government will impose financial penalties (up to ₹5 crore per violation) on platforms that fail to enforce anti‑spam provisions in RCS. This will trigger a wave of third‑party compliance tools – automated grievance trackers, RCS traffic analysers as a service, and zero‑trust business messaging gateways. Simultaneously, users will migrate toward decentralised alternatives like Matrix or Signal, which lack the commercial incentive to tolerate spam. Google will be forced to open‑source its RCS spam classifier and allow client‑side blocking, shifting power from business senders back to consumers.
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