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Email Threat Intelligence: Extending SATIS Beyond IP Addresses

IP addresses are only half the story. The majority of successful breaches still start with an email: a credential phishing link, a malware-laden attachment, or a business email compromise from a freshly registered domain. Blocking malicious IPs at the firewall is necessary but insufficient when the attacker's most effective weapon arrives in an inbox.

SATIS now extends its real-time threat intelligence pipeline to cover email-based threats. The same blockchain-backed, multi-source approach that powers our IP threat feeds now applies to email address blacklists, DNS RPZ zones for mail servers, and message hash fingerprinting for phishing detection.

Why Email Threats Need Real-Time Intelligence

Traditional email security relies on static blocklists and signature-based scanning. These approaches share a fundamental weakness: they are reactive. A phishing campaign can send thousands of messages in the first 15 minutes after a domain is registered, long before it appears on any blocklist.

SATIS addresses this with the same sub-30-second distribution model used for IP threats. When a malicious email address or sending domain is identified — whether by automated collectors, fail2ban mail filters, or customer reports — it is published to the blockchain and distributed to all subscribers in the next block cycle. Mail servers pulling from the SATIS email feed get protection within seconds, not hours.

Email Address Blacklist

The core of email threat intelligence is a curated blacklist of addresses and domains observed in malicious activity. SATIS aggregates email threat data from multiple sources:

• Spam trap networks that capture addresses actively sending unsolicited or malicious mail
• Customer-reported phishing from organizations that submit confirmed phishing sender addresses via the API
• Honeypot mail servers that log connection attempts from compromised accounts and botnet relays
• Cross-correlation with IP threats — when an IP in the SATIS threat database is also observed as a mail relay, the associated sender addresses are flagged

Each entry includes confidence scoring using the same multi-source adjustment engine that powers IP threat scoring. An address reported by three independent sources scores higher than a single spam trap hit. Source reliability weights ensure that verified phishing reports carry more weight than automated detections.

The blacklist is available via the existing REST API with a new type=email filter parameter, and through STIX 2.1 bundles with email-specific indicator patterns.

DNS RPZ for Mail Servers

For organizations running their own mail infrastructure, DNS Response Policy Zones (RPZ) provide a powerful enforcement mechanism. SATIS generates RPZ zone files that mail servers can consume directly, causing DNS lookups for malicious sending domains to return NXDOMAIN or redirect to a sinkhole.

This works at the MTA level, before message content is even evaluated:

; SATIS Email Threat RPZ Zone
; Generated: 2026-03-03T00:00:00Z
; Entries: 4,218 malicious sending domains

malicious-sender.example.    CNAME .    ; NXDOMAIN
phishing-campaign.biz.       CNAME .    ; NXDOMAIN
compromised-relay.net.       CNAME rpz-sinkhole.setecastronomyinc.com.

The RPZ zone is updated with each block cycle and available as a zone transfer (AXFR/IXFR) for BIND, Unbound, and PowerDNS. Professional and Enterprise subscribers can configure their resolvers to pull incremental updates, keeping their mail server DNS protection current within seconds of a new threat being published.

This is the same approach used by large-scale DNS filtering services, but backed by SATIS blockchain consensus rather than a single vendor's proprietary database.

Message Hash Fingerprinting

Phishing campaigns frequently reuse message templates with minor variations — swapping the target URL or the sender name while keeping the body structure identical. SATIS computes fuzzy hashes (ssdeep-style similarity digests) of reported phishing messages, enabling detection of campaign variants even when specific indicators change.

The fingerprinting process works in three stages:

1. Normalization — strip headers, decode MIME, extract the text and HTML body
2. Hashing — compute a similarity digest of the normalized content, tolerant of minor edits like URL swaps or name personalization
3. Matching — compare incoming message hashes against the SATIS fingerprint database, returning a similarity score

A similarity score above 85% flags the message as a likely variant of a known phishing campaign. This catches the second, third, and tenth wave of a campaign that traditional signature matching misses because the specific URLs have changed.

Message hashes are published to the blockchain alongside the original threat entry, so all subscribers benefit from every confirmed phishing report.

Integration with the Existing Platform

Email threat intelligence slots into the same architecture that handles IP threats:

• API access via GET /api/v1/threats?type=email with the same authentication and rate limits
• STIX 2.1 indicators with pattern_type: stix and email-address observable patterns
• SIEM export in CEF, LEEF, Splunk HEC, and Sentinel formats with email-specific field mappings
• Webhook notifications for threat.added events that include email threat metadata
• Confidence scoring using the same multi-source adjustment engine, extended with email-specific source weights

For mail server administrators, the DNS RPZ integration requires no application-level changes — configure your resolver to use the SATIS RPZ zone and enforcement happens transparently at the DNS layer.

Availability

Email threat feeds are available on Professional and Enterprise plans. The RPZ zone transfer, message hash API, and email-specific STIX indicators are all included at no additional cost for existing subscribers.

See the API documentation for endpoint details, or visit the services page for plan comparison.

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