DNS tunneling is a real threat, but not every long or messy hostname hides a covert channel. Some are simply the side-effect of misconfigurations inside normal business infrastructure. In this post we examine two real patterns our ThreatSTOP sensors captured. One is a noisy but harmless search-suffix loop that lives entirely inside a corporate namespace. The other shows hallmarks of an active tunnel. Seeing them together highlights why context and correlation matter.  We've redacted that actual name of the company in the "Pattern 1" example.

Pattern 1 – the corporate echo

12101c31ne.12101c31ne.12101c31ne.… (15 copies) …divpnframin.12101c31ne.jss2.tscmtapssnd1.sv.[redacted].com

What is happening

Component

Likely meaning

12101c31ne

Maybe device hostname. Ten characters packed with internal codes.

divpnframin or divpnwestin

Maybe VPN hub identifiers. Framin may point to a Framingham MA campus. Westin may refer to the Westin carrier hotel data center in Seattle WA.

jss2

Perhaps Jamf Software Server cluster two, used for Apple fleet management.

tscmtapssnd1

Probably Tech Services Client Management Tap Sensor Node one. A collector that logs DNS, DHCP, and proxy events.

sv.[redacted].com

Internal service zone hosted on authoritative BIND clusters in Framingham and Seattle.

 

Why it appears fifteen times

  1. The client hostname is 12101c31ne.

  2. The VPN profile pushes a search suffix that already begins with the same hostname:

    divpnframin.12101c31ne.jss2.tscmtapssnd1.sv.[redacted].com

  3. The resolver tries 12101c31ne first. When that fails, it prepends the query to the entire search suffix and retries, repeating up to fifteen times or until the name exceeds 255 bytes.

  4. Each retry adds another copy of the hostname, producing the chain you see.


Impact on the resolver

  • Thousands of NXDOMAIN replies during login storms.

  • Little to no payload risk because the traffic never leaves [redacted].com, uses only A and AAAA types, and stops once the system is fully online.

Pattern 2 – a likely DNS tunnel

mubar6zlo2ntpy2wkczifjkzl2vvcaaaatffsaqawaeqaaetauaaa2qaaaac64h.
nsboiuz7mcc6bef6ycj477v4r477vk22i36kyo63zrchigan4yleaikeztmdldm.
smjifytqsvi42odyhck7x2k6f5n3bessoclsmbnbm5l652szwa6rcxbugestsuf.
nyvb7vjcuscbbgbrvtma4aarlxu3w5j36oxxmfnw.ns-watchde.zivpn.com.

 

Red flags

  • Labels use Base32 or Base64 style text that maximizes data per character.

  • Four labels carry roughly 180 bytes, ideal for transferring encrypted payloads.

  • Parent domain ns-watchde.zivpn.com is obscure, wildcarded, and recently registered.

  • Record type is often TXT or NULL, common choices for tunneling frameworks.

  • Queries arrive at a steady cadence that resembles a heartbeat channel.

Side-by-side comparison

 

Attribute

Search-suffix loop

Likely tunnel

Parent zone

Internal ([redacted].com)

External and unknown

Label content

Exact hostname repeats

High-entropy encoding

Leftmost label

Static

Changes each query

RR type

A or AAAA

TXT, NULL, or CNAME

TTL pattern

Corporate standard

Very short or zero

Data volume

Bursts at boot

Continuous trickle

Risk level

Low

High

 

How ThreatSTOP handles each case

DNS Defense Cloud and DNS Defense evaluate every query against thousands of curated threat feeds plus real-time intelligence from the ThreatSTOP Security, Intelligence, and Research team.

  • For Pattern 1: the engine recognizes that all queries stay inside a known zone, use low-risk record types, and carry no entropy. The event is logged for visibility but traffic is allowed.

  • For Pattern 2: the engine scores high entropy, unknown zone, and risky record types. The domain is blocked instantly and, if using IP Defense, the controlling server’s addresses are denied across firewalls, routers, and cloud edge devices.

Analyst playbook

  1. Check the zone. Internal domains rarely host tunnels.

  2. Count entropy. Long runs of a-z2-7 or mixed case Base64 need attention.

  3. Watch record types. Sudden TXT bursts are a strong warning.

  4. Correlate with endpoint logs. A single host uploading data in step with the DNS flow confirms a compromise.

  5. Fix the noise. For loops like Pattern 1, correct DHCP option 119 or lower ndots, then push the change with your MDM.

Conclusion

Long or complex DNS hostnames deserve scrutiny, but context determines their true nature. ThreatSTOP protection gives you that context, correlating domain reputation, entropy, record type, and network history in real time. The result is clear: real tunnels are blocked, harmless echoes glide through, and your analysts stay focused on genuine threats.

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