TCP SYN (p0f)

4:39+25:0:1400:mss*20,7:mss,sok,ts,nop,ws:df,id+:0

first seen 2026-06-14 17:28 · last seen 2026-06-14 17:29 · JSON

Inconsistencies

User-Agents observed with this fingerprint that contradict what it proves at the wire. all inconsistencies →

fingerprint User-Agent claims wire shows confidence seen first seen last seen

4:39+25:0:1400:mss*20,7:mss,sok,ts,nop,ws:df,id+:0

Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 …

User-Agent claims Windows

TCP SYN initial TTL 39+25 indicates Unix-like

The initial TTL is set by the sending kernel (64 on Unix-like systems, 128 on Windows) and survives NAT. But VPNs, proxies and tunnels legitimately replace the sending stack, so this check never exceeds medium confidence.

Full User-Agent	Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36
Observed TTL	39+25 (observed + path distance → initial)
Claimed OS	Windows
Confidence	medium — repeated co-occurrence, but initial TTL is environmental — capped at medium

medium

2026-06-14

Decomposed attributes

IP version	`4`
Initial TTL	`39+25`
Options length	`0`
MSS	`1400`
Window size	`mss*20`
Window scale	`7`
Options layout	`mss,sok,ts,nop,ws`
Quirks	`df,id+`
Payload class	`0`

Co-observed signals

Signals from other families seen in the same observation. A fingerprint spread thinly across many lower-layer signatures is a classic inconsistency signal.

TLS ClientHello (JA4)

fingerprint	co-occurrences
`t13d191000_9dc949149365_e7c285222651`	3

HTTP request (JA4H)

fingerprint	co-occurrences
`ge11nn020000_3ed38b250d3d_000000000000_000000000000`	3

User-Agent

fingerprint	co-occurrences
`Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36`	3

Country

fingerprint	co-occurrences
`CN` · China	3

Network (ASN)

fingerprint	co-occurrences
`AS4134` · CHINANET BACKBONE	3