Why is Google flagging my CDN or email content as malicious?

Key findings

• Malware Detection: Google’s systems are designed to detect malware, phishing, and other harmful content. If your CDN hosts compromised files or your email content contains suspicious links or scripts, it will be flagged to protect users.
• Reputation-Based Flagging: A history of abusive content, spam, or security incidents linked to your domain or IP address can lead to Google proactively flagging your content. This is closely tied to your domain reputation.
• CDN Vulnerabilities: Even reputable CDNs (content delivery networks) like AWS can serve malicious content if the origin server is compromised or if configurations allow for injection of harmful elements.
• Deceptive Content: Warnings can be triggered by social engineering tactics within your email or website, such as deceptive links (e.g., a display URL that differs from the actual destination) or pop-ups that trick users into revealing information.
• Mixed Content: For websites using HTTPS, loading content (like images or scripts) over an insecure HTTP connection can trigger browser warnings, implying a security risk.

Key considerations

• Thorough Auditing: Conduct a comprehensive audit of your website and email content for any signs of compromise, malicious scripts, or suspicious redirects. This includes checking all external resources loaded via your CDN.
• Google Search Console: Utilize Google Search Console’s Security Issues report to identify specific URLs or content flagged as problematic, as this is where Google provides direct notifications.
• Content Review: Scrutinize email creatives for any non-standard elements, such as IP addresses in links or excessively long tracking URLs, which can sometimes trigger spam filters and malicious flags.
• Email Authentication: Ensure your email sending domain has robust SPF, DKIM, and DMARC records properly configured. This helps establish trust and verifies your sending legitimacy. Hosting images on your sending domain (with proper authentication) is also recommended.
• Remediation and Review: After cleaning up identified issues, request a review from Google. For website issues, this is done via Google Search Console. For email, continuous monitoring of deliverability and domain reputation is key. More information can be found on how to resolve a "deceptive site ahead" warning.

Key opinions

• Google's Aggressiveness: Many marketers feel that Google has recently become "trigger happy" with its malicious content warnings, indicating a potential shift in their detection algorithms.
• CDN Specifics: Using CDNs like AWS S3 buckets (especially without proper CNAME setup) has been directly linked by some marketers to Google's flagging issues.
• Tracking Link Sensitivity: Overly long or numeric tracking links are seen as a potential trigger for warnings, suggesting Google's filters scrutinize link structure closely.
• Impact on Deliverability: Flagged content can lead to significant drops in email deliverability, pushing emails to spam or blocking them entirely.

Key considerations

• CDN Configuration: Marketers recommend reviewing CDN configurations, particularly for custom domains and CNAME setups, to ensure proper domain alignment.
• Image Hosting: Consider hosting images directly on your ESP's infrastructure or ensuring your own image hosting aligns with your sending domain to prevent flagging.
• Tracking Link Optimization: Shortening tracking links or making them less numeric might help avoid Google's filters. This also plays a role in preventing suspicious link warnings.
• CDN Support: Engaging with CDN customer support (e.g., AWS) is often recommended, as they might have more data and insights into why specific content is being flagged.

Key opinions

• Reputation is Key: Expert from Email Geeks suggests that flagging is often reputation-based, indicating that historical sending practices heavily influence Google's trust in your content.
• IP Addresses in Creative: Direct inclusion of IP addresses within email creative (e.g., in links or images) is a common trigger for malicious warnings, according to experts.
• Domain Mismatch Concerns: Experts warn that domain mismatches, where visible link text doesn't align with the actual destination URL, are a significant red flag for anti-phishing filters.
• Authentication Importance: Proper SPF and DKIM authentication are critical; images and other linked content should ideally be hosted on a domain that passes these checks.
• Bounce Management: Ensuring sender and reply-to addresses do not bounce is vital, as high bounce rates can negatively impact sender reputation and trigger warnings.

Key considerations

• Content Hygiene: Regularly clean your email content of any elements that could be misconstrued as malicious, such as hidden text, suspicious redirects, or overly complex tracking.
• Sender Identity: Ensure that your email's sender identity (from, reply-to) is consistent and legitimate to build a trustworthy reputation with ISPs.
• Domain Alignment: Experts stress the importance of maintaining proper domain alignment for all links and images within your emails, consistent with your sending domain, to avoid phishing detections.
• Proactive Monitoring: Implement continuous monitoring of your email deliverability and any blacklist status, as early detection is crucial for quick resolution. Understanding Spamresource.com can provide valuable insight on this.

Key findings

• Malware/Hacked Sites: Google warning messages are primarily designed to alert users about websites that have been hacked or contain malware, viruses, or other harmful software.
• Social Engineering & Phishing: Content that attempts to trick users into revealing personal information (phishing) or installing unwanted software falls under social engineering guidelines, triggering "deceptive site ahead" warnings.
• Compromised Third-Party Resources: Inclusion of malicious third-party resources, such as compromised ad networks or external pop-ups within your email or website content, can lead to flagging.
• HTTPS/HTTP Mixed Content: Even on secure HTTPS websites, loading any content over an insecure HTTP connection can cause Google (or browsers) to display security warnings.

Key considerations

• Regular Security Scans: Documentation advises frequent security scans of your website and server environment to detect and remove any malware or unauthorized content promptly.
• Content Compliance: Review Google’s Safe Browsing guidelines on social engineering and deceptive content to ensure your emails and landing pages adhere to their policies.
• Source Verification: Verify the legitimacy and security of all third-party scripts, ads, or content (e.g., from CDNs) included in your emails or on your website.
• HTTPS Implementation: Ensure all resources on an HTTPS site are also loaded securely via HTTPS to avoid mixed content warnings.
• Remediation Process: Follow the documented process for requesting a review after fixing issues, typically through Google Search Console for websites or through improved sending practices for emails.