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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>AWS Transit Gateway Security | AWS Security Cards</title>
<meta name="description" content="Transit Gateway (TGW) is a network hub connecting VPCs, VPNs, and Direct Connect. Route manipulation can destroy network segmentation, enable traffic interception, and provide lateral movement across accounts.">
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</head>
<body>
<!-- Card Image -->
<div class="card-image">
<img src="../images/transitgateway-card.webp" alt="AWS Transit Gateway Security" />
</div>
<!-- Header -->
<div class="header">
<div class="header-content">
<div class="header-icon"><img src="../icons/transitgateway.svg" alt="AWS Transit Gateway Security" /></div>
<div>
<div>
<span class="header-title">AWS Transit Gateway Security</span>
<span class="header-badge">NETWORK TRANSIT</span>
</div>
<p class="header-desc">Transit Gateway (TGW) is a network hub connecting VPCs, VPNs, and Direct Connect. Route manipulation can destroy network segmentation, enable traffic interception, and provide lateral movement across accounts.</p>
</div>
</div>
</div>
<!-- Stats -->
<div class="stats-row">
<div class="stat-card">
<div class="stat-value" style="color: #f87171;">No Deny</div>
<div class="stat-label">Route Tables</div>
</div>
<div class="stat-card">
<div class="stat-value" style="color: #4ade80;">Cross-Acct</div>
<div class="stat-label">Via RAM</div>
</div>
<div class="stat-card">
<div class="stat-value" style="color: #60a5fa;">5000</div>
<div class="stat-label">Max Attachments</div>
</div>
<div class="stat-card">
<div class="stat-value" style="color: #c084fc;">No Logs</div>
<div class="stat-label">By Default</div>
</div></div>
<!-- Overview -->
<div class="section"><h2><span style="color:#06b6d4;">📋</span> Service Overview</h2><div class="overview-grid">
<div>
<h4 style="color: #06b6d4;">Route Tables & Propagation</h4>
<p>TGW route tables control traffic flow between attachments. Route propagation automatically learns routes from VPCs and VPNs. A single shared route table with propagation enabled creates a full mesh network, destroying all segmentation.</p>
</div>
<div>
<h4 style="color: #06b6d4;">Attachments & Sharing</h4>
<p>TGW connects VPCs, VPN connections, Direct Connect gateways, and TGW peering. Cross-account sharing via RAM allows other accounts to attach their VPCs. There is no concept of "deny" in TGW route tables - only allow or blackhole.</p>
</div>
<div>
<h4 style="color: #06b6d4;">Inter-Region Peering</h4>
<p>TGW peering connects transit gateways across regions, enabling global routing. A compromised TGW in one region can be peered to reach networks in other regions, amplifying the blast radius of a network compromise significantly.</p>
</div></div></div>
<!-- Risk Assessment -->
<div class="section">
<h2>Security Risk Assessment</h2>
<div class="risk-gauge">
<div class="risk-bar-container">
<div class="risk-bar">
<div class="risk-bar-fill" style="width: 85%;"></div>
</div>
<div class="risk-labels"><span>Low</span><span>Medium</span><span>High</span><span>Critical</span></div>
</div>
<div class="risk-score">
<div class="risk-score-value">8.5</div>
<div class="risk-score-label">Risk Score</div>
</div>
</div>
<p class="risk-desc">Transit Gateway controls routing for the entire network. Route manipulation destroys segmentation, blackhole deletion re-enables blocked traffic, and TGW flow logs are not enabled by default leaving no audit trail.</p>
</div>
<!-- Main Panels -->
<div class="panels-grid">
<div class="panel" style="border-color: #f8717133;">
<h3 style="color: #f87171;">⚔️ Attack Vectors</h3><h4 style="color: #f87171;">Route Manipulation</h4><ul><li><span class="bullet" style="color: #f87171;">•</span> Create routes to redirect traffic through attacker VPC</li><li><span class="bullet" style="color: #f87171;">•</span> Replace existing routes to intercept sensitive traffic</li><li><span class="bullet" style="color: #f87171;">•</span> Delete blackhole routes to re-enable blocked connectivity</li><li><span class="bullet" style="color: #f87171;">•</span> Enable route propagation for full mesh access</li><li><span class="bullet" style="color: #f87171;">•</span> VPN route injection from compromised VPN connection</li></ul><h4 style="color: #f87171;">Network Expansion</h4><ul><li><span class="bullet" style="color: #f87171;">•</span> Create TGW peering attachment for cross-region access</li><li><span class="bullet" style="color: #f87171;">•</span> Attach attacker VPC to shared Transit Gateway</li><li><span class="bullet" style="color: #f87171;">•</span> Modify route table associations to gain access</li><li><span class="bullet" style="color: #f87171;">•</span> Cross-account pivot via RAM-shared TGW</li><li><span class="bullet" style="color: #f87171;">•</span> Direct Connect gateway attachment for on-premises access</li></ul></div>
<div class="panel" style="border-color: #fb923c33;">
<h3 style="color: #fb923c;">⚠️ Misconfigurations</h3><h4 style="color: #fb923c;">Routing Issues</h4><ul><li><span class="bullet" style="color: #fb923c;">•</span> Single route table for all VPCs (no segmentation)</li><li><span class="bullet" style="color: #fb923c;">•</span> Auto-propagation enabled on all route tables</li><li><span class="bullet" style="color: #fb923c;">•</span> No blackhole routes for sensitive CIDRs</li><li><span class="bullet" style="color: #fb923c;">•</span> Default route table association for new attachments</li><li><span class="bullet" style="color: #fb923c;">•</span> Overlapping CIDRs causing routing conflicts</li></ul><h4 style="color: #fb923c;">Monitoring Gaps</h4><ul><li><span class="bullet" style="color: #fb923c;">•</span> TGW flow logs not enabled (not on by default)</li><li><span class="bullet" style="color: #fb923c;">•</span> No alerts on route table changes</li><li><span class="bullet" style="color: #fb923c;">•</span> RAM sharing without restriction on who can attach</li><li><span class="bullet" style="color: #fb923c;">•</span> No network segmentation validation</li><li><span class="bullet" style="color: #fb923c;">•</span> Peering attachments not audited</li></ul></div>
<div class="panel" style="border-color: #22d3ee33;">
<h3 style="color: #22d3ee;">🔍 Enumeration</h3>
<div class="cmd-block">
<div class="cmd-title">List Transit Gateways</div>
<pre><code>aws ec2 describe-transit-gateways</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">List Route Tables</div>
<pre><code>aws ec2 describe-transit-gateway-route-tables \\
--filters Name=transit-gateway-id,Values=tgw-0123456789abcdef</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Search Routes</div>
<pre><code>aws ec2 search-transit-gateway-routes \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--filters Name=state,Values=active</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">List Attachments</div>
<pre><code>aws ec2 describe-transit-gateway-attachments \\
--filters Name=transit-gateway-id,Values=tgw-0123456789abcdef</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">List Peering Attachments</div>
<pre><code>aws ec2 describe-transit-gateway-peering-attachments</code></pre>
</div></div>
<div class="panel" style="border-color: #c084fc33;">
<h3 style="color: #c084fc;">🚨 Key Concepts</h3><h4 style="color: #c084fc;">No Deny in TGW Route Tables</h4><ul><li><span class="bullet" style="color: #c084fc;">•</span> TGW route tables only have active routes and blackhole routes</li><li><span class="bullet" style="color: #c084fc;">•</span> No deny rules like NACLs or security groups</li><li><span class="bullet" style="color: #c084fc;">•</span> Blackhole routes drop traffic but can be deleted by attacker</li><li><span class="bullet" style="color: #c084fc;">•</span> Route specificity determines which route wins (longest prefix)</li><li><span class="bullet" style="color: #c084fc;">•</span> A more specific route overrides broader blackhole routes</li></ul><h4 style="color: #c084fc;">Blast Radius Amplification</h4><ul><li><span class="bullet" style="color: #c084fc;">•</span> Single TGW connects hundreds of VPCs across accounts</li><li><span class="bullet" style="color: #c084fc;">•</span> Route propagation enables auto-discovery of all connected networks</li><li><span class="bullet" style="color: #c084fc;">•</span> Cross-region peering extends reach to other AWS regions</li><li><span class="bullet" style="color: #c084fc;">•</span> VPN attachment routes can be injected from on-premises</li><li><span class="bullet" style="color: #c084fc;">•</span> Compromising TGW admin = compromising the entire network</li></ul></div>
<div class="panel" style="border-color: #facc1533;">
<h3 style="color: #facc15;">⚡ Persistence Techniques</h3><h4 style="color: #facc15;">Route Persistence</h4><ul><li><span class="bullet" style="color: #facc15;">•</span> Add static routes pointing to attacker VPC attachment</li><li><span class="bullet" style="color: #facc15;">•</span> Enable propagation to auto-learn new VPC routes</li><li><span class="bullet" style="color: #facc15;">•</span> Create additional route table with permissive routing</li><li><span class="bullet" style="color: #facc15;">•</span> Associate target VPC attachments with attacker route table</li><li><span class="bullet" style="color: #facc15;">•</span> Create peering attachment for out-of-band access path</li></ul><h4 style="color: #facc15;">Attachment Persistence</h4><ul><li><span class="bullet" style="color: #facc15;">•</span> Attach attacker VPC to Transit Gateway via RAM share</li><li><span class="bullet" style="color: #facc15;">•</span> Create VPN attachment for persistent external access</li><li><span class="bullet" style="color: #facc15;">•</span> Modify existing route table associations subtly</li><li><span class="bullet" style="color: #facc15;">•</span> Add routes that survive attachment deletion</li><li><span class="bullet" style="color: #facc15;">•</span> Cross-account attachment remains after RAM share revoked</li></ul></div>
<div class="panel" style="border-color: #4ade8033;">
<h3 style="color: #4ade80;">🛡️ Detection</h3><h4 style="color: #4ade80;">CloudTrail Events</h4><ul><li><span class="bullet" style="color: #4ade80;">•</span> CreateTransitGatewayRoute - new route added to TGW route table</li><li><span class="bullet" style="color: #4ade80;">•</span> ReplaceTransitGatewayRoute - existing route modified</li><li><span class="bullet" style="color: #4ade80;">•</span> DeleteTransitGatewayRoute - blackhole route removed</li><li><span class="bullet" style="color: #4ade80;">•</span> CreateTransitGatewayPeeringAttachment - peering created</li><li><span class="bullet" style="color: #4ade80;">•</span> AssociateTransitGatewayRouteTable - association changed</li></ul><h4 style="color: #4ade80;">Indicators of Compromise</h4><ul><li><span class="bullet" style="color: #4ade80;">•</span> Unexpected route additions to TGW route tables</li><li><span class="bullet" style="color: #4ade80;">•</span> Blackhole routes deleted without change ticket</li><li><span class="bullet" style="color: #4ade80;">•</span> New VPC attachments from unknown accounts</li><li><span class="bullet" style="color: #4ade80;">•</span> Peering attachments to unknown regions</li><li><span class="bullet" style="color: #4ade80;">•</span> Route propagation enabled on isolated route tables</li></ul></div></div>
<!-- Exploitation -->
<div class="section"><h2><span style="color:#f87171;">💻</span> Exploitation Commands</h2><div class="cmd-grid">
<div class="cmd-block">
<div class="cmd-title">Create Route to Redirect Traffic</div>
<pre><code>aws ec2 create-transit-gateway-route \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--destination-cidr-block 10.0.0.0/8 \\
--transit-gateway-attachment-id tgw-attach-attacker</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Replace Existing Route</div>
<pre><code>aws ec2 replace-transit-gateway-route \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--destination-cidr-block 10.1.0.0/16 \\
--transit-gateway-attachment-id tgw-attach-attacker</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Delete Blackhole Route</div>
<pre><code>aws ec2 delete-transit-gateway-route \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--destination-cidr-block 10.99.0.0/16</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Enable Route Propagation (Full Mesh)</div>
<pre><code>aws ec2 enable-transit-gateway-route-table-propagation \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--transit-gateway-attachment-id tgw-attach-prod-vpc</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Create Peering Attachment (Cross-Region)</div>
<pre><code>aws ec2 create-transit-gateway-peering-attachment \\
--transit-gateway-id tgw-source \\
--peer-transit-gateway-id tgw-target \\
--peer-region eu-west-1 \\
--peer-account-id 123456789012</code></pre>
</div>
<div class="cmd-block">
<div class="cmd-title">Map All Connected Networks</div>
<pre><code>for rtb in $(aws ec2 describe-transit-gateway-route-tables --query 'TransitGatewayRouteTables[].TransitGatewayRouteTableId' --output text); do
echo "=== Route Table: $rtb ==="
aws ec2 search-transit-gateway-routes --transit-gateway-route-table-id $rtb --filters Name=state,Values=active --query 'Routes[].[DestinationCidrBlock,TransitGatewayAttachments[0].ResourceId]' --output table
done</code></pre>
</div></div></div>
<!-- Policies -->
<div class="section"><h2><span style="color:#4ade80;">📜</span> Policy Examples</h2><div class="policy-grid">
<div class="policy-card" style="border-color: #ef444433; background: rgba(239,68,68,0.05);">
<div class="policy-header">
<span style="color: #f87171; font-size: 1.2em;">✗</span>
<span style="color: #f87171; font-weight: 600;">Dangerous - Full TGW Route Control</span>
</div>
<pre><code>{
"Version": "2012-10-17",
"Statement": [{
"Effect": "Allow",
"Action": [
"ec2:CreateTransitGatewayRoute",
"ec2:ReplaceTransitGatewayRoute",
"ec2:DeleteTransitGatewayRoute",
"ec2:*TransitGateway*"
],
"Resource": "*"
}]
}</code></pre>
<p class="policy-desc">Full TGW access allows route manipulation, blackhole deletion, and cross-region peering creation</p>
</div>
<div class="policy-card" style="border-color: #22c55e33; background: rgba(34,197,94,0.05);">
<div class="policy-header">
<span style="color: #4ade80; font-size: 1.2em;">✓</span>
<span style="color: #4ade80; font-weight: 600;">Secure - Read-Only Network Monitoring</span>
</div>
<pre><code>{
"Version": "2012-10-17",
"Statement": [{
"Effect": "Allow",
"Action": [
"ec2:DescribeTransitGateways",
"ec2:DescribeTransitGatewayRouteTables",
"ec2:SearchTransitGatewayRoutes",
"ec2:DescribeTransitGatewayAttachments"
],
"Resource": "*"
}]
}</code></pre>
<p class="policy-desc">Read-only access for network monitoring without route modification capabilities</p>
</div>
<div class="policy-card" style="border-color: #ef444433; background: rgba(239,68,68,0.05);">
<div class="policy-header">
<span style="color: #f87171; font-size: 1.2em;">✗</span>
<span style="color: #f87171; font-weight: 600;">Dangerous - Can Delete Blackhole Routes</span>
</div>
<pre><code>{
"Version": "2012-10-17",
"Statement": [{
"Effect": "Allow",
"Action": [
"ec2:DeleteTransitGatewayRoute",
"ec2:EnableTransitGatewayRouteTablePropagation"
],
"Resource": "*"
}]
}</code></pre>
<p class="policy-desc">Deleting blackhole routes re-enables blocked traffic, and enabling propagation creates full mesh</p>
</div>
<div class="policy-card" style="border-color: #22c55e33; background: rgba(34,197,94,0.05);">
<div class="policy-header">
<span style="color: #4ade80; font-size: 1.2em;">✓</span>
<span style="color: #4ade80; font-weight: 600;">Secure - SCP Restrict Route Changes</span>
</div>
<pre><code>{
"Version": "2012-10-17",
"Statement": [{
"Sid": "DenyTGWRouteChanges",
"Effect": "Deny",
"Action": [
"ec2:CreateTransitGatewayRoute",
"ec2:ReplaceTransitGatewayRoute",
"ec2:DeleteTransitGatewayRoute",
"ec2:CreateTransitGatewayPeeringAttachment"
],
"Resource": "*",
"Condition": {
"StringNotEquals": {
"aws:PrincipalArn": "arn:aws:iam::*:role/NetworkAdmin"
}
}
}]
}</code></pre>
<p class="policy-desc">SCP restricts TGW route changes to a dedicated NetworkAdmin role only</p>
</div></div></div>
<!-- Defenses -->
<div class="section"><h2><span style="color:#4ade80;">🛡️</span> Defense Recommendations</h2><div class="defense-grid">
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">🔒</span>
<div>
<h4>Separate Route Tables Per Security Domain</h4>
<p>Use isolated route tables for production, development, and shared services. Never use a single route table for all VPCs.</p>
</div>
</div>
</div>
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">🚫</span>
<div>
<h4>Disable Auto-Propagation</h4>
<p>Disable route propagation and use static routes only. Auto-propagation creates full mesh that breaks segmentation.</p>
<pre><code>aws ec2 disable-transit-gateway-route-table-propagation \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--transit-gateway-attachment-id tgw-attach-vpc</code></pre>
</div>
</div>
</div>
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">📡</span>
<div>
<h4>Enable TGW Flow Logs</h4>
<p>TGW flow logs are not enabled by default. Enable them to detect traffic anomalies and unauthorized routing.</p>
<pre><code>aws ec2 create-flow-logs \\
--resource-type TransitGateway \\
--resource-ids tgw-abc123 \\
--traffic-type ALL \\
--log-destination-type s3 \\
--log-destination arn:aws:s3:::flow-logs-bucket</code></pre>
</div>
</div>
</div>
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">🕳️</span>
<div>
<h4>Blackhole Unused CIDRs</h4>
<p>Add blackhole routes for CIDRs that should never be routable to prevent lateral movement.</p>
<pre><code>aws ec2 create-transit-gateway-route \\
--transit-gateway-route-table-id tgw-rtb-abc123 \\
--destination-cidr-block 10.99.0.0/16 \\
--blackhole</code></pre>
</div>
</div>
</div>
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">🔔</span>
<div>
<h4>Alert on Route Table Changes</h4>
<p>Create EventBridge rules for CreateTransitGatewayRoute, DeleteTransitGatewayRoute, and peering changes.</p>
</div>
</div>
</div>
<div class="defense-card">
<div class="defense-header">
<span class="defense-icon">🏢</span>
<div>
<h4>Restrict RAM Sharing</h4>
<p>Control which accounts can attach to the TGW via RAM resource share permissions and SCPs.</p>
</div>
</div>
</div></div></div>
<!-- Footer -->
<div class="footer">
<p>AWS Transit Gateway Security Card</p>
<p style="margin-top:0.25rem;">Always obtain proper authorization before testing</p>
</div>
</body>
</html>