Scfilter - Cid87d25e32ac0d4ef0b1e0502c6b7dfb77

Various tools for file operations, such as access protection by encryption or copying and synchronizing (Product group: Security software & Suites)

Remember that not only company computers contain data that should be protected from unauthorized access. Through encryption, important files can also be protected on privately used computers with this collection of tools. Passwords, USB sticks, various chip cards or certificates can be used as keys. As additional security, a password scrambler prevents key loggers from reading the keyboard input. The data encrypted with AES or Blowfish can only be opened with the correct key. In addition, the software offers the possibility to sign files, create a backup or synchronize data. The software is operated directly in the Windows File Explorer or alternatively via an assistant

Scfilter - Cid87d25e32ac0d4ef0b1e0502c6b7dfb77

The keyword scfilter\cid87d25e32ac0d4ef0b1e0502c6b7dfb77 refers to a specific Hardware ID for a Generic Smart Card device as recognized by the Windows operating system. Specifically, it is the identifier used by the Smart Card PnP Class Filter Driver (scfilter.sys) to manage the communication between a smart card and its reader. Understanding SCFILTER and Smart Card IDs

In Windows, when you insert a smart card (like a security token, employee ID, or cryptographic card) into a reader, the system needs to identify what kind of card it is to load the correct driver.

SCFILTER: This is the "Smart Card PnP Class Filter Driver". It sits on top of the card reader driver to detect when a card is inserted and helps generate a Plug and Play (PnP) ID for that card.

CID (Card Identifier): The string following "SCFILTER" is a unique ID generated from the card’s Answer to Reset (ATR) string.

CID_87D25E32AC0D4EF0B1E0502C6B7DFB77: This specific hex string identifies a "Generic Smart Card" often found in systems manufactured by companies like Gigabyte. Why You See This ID scfilter cid87d25e32ac0d4ef0b1e0502c6b7dfb77

You likely encountered this code because of one of the following scenarios:

Device Manager Issues: A "Smart Card" appears in your Device Manager with a yellow exclamation mark because the system cannot find a specific "Minidriver" for it.

Driver Scanning: Tools like DriverIdentifier or DriverPack often flag this ID when searching for missing system drivers.

Security Software Flags: Occasionally, security scanners like Norton Power Eraser may flag scfilter.sys as a potential threat, though this is usually a false positive as it is a legitimate Microsoft system file. How to Resolve Missing Driver Errors Have you encountered a strange filter ID in your logs

If your computer is asking for a driver for this specific CID, it usually means the card you inserted requires a Smart Card Minidriver. DriverIdentifierhttps://www.driveridentifier.com

The Takeaway

Identifiers like scfilter cid87d25e32ac0d4ef0b1e0502c6bdfb77 are usually harmless—they’re just breadcrumbs left by security systems to help administrators understand why content was filtered. But they’re also a good reminder that most of what we do online is classified, logged, and labeled by machines. Stay curious, but don’t panic when you see a random hash. It’s probably just your friendly neighborhood content filter doing its job.

Have you encountered a strange filter ID in your logs? Share your experience in the comments below.

2. Rule Behavior

scfilter operates on reassembled TCP streams, not individual packets.
It can inspect data that spans multiple packets, making evasion techniques like TCP segmentation harder to bypass.
The CID (87d25e32ac0d4ef0b1e0502c6b7dfb77) likely maps to a specific signature / pattern database entry inside Suricata’s scfilter module.

Why Would You See It?

You might encounter scfilter cid87d25e32ac0d4ef0b1e0502c6b7dfb77 in: email attachment hash

Email headers – If your corporate mail server flagged a message with a certain content ID.
Web proxy logs – Showing that a request matched a content filter rule.
Security software alerts – As a reference code for a blocked threat.
Browser developer tools – If a page element was blocked by an extension or firewall.

Breaking Down the String

scfilter – The module or system (Security Content Filter)
cid – Content / Classification Identifier
87d25e32ac0d4ef0b1e0502c6b7dfb77 – A 32-character hexadecimal string (looks like an MD5 hash or UUID)

This hash is likely generated from a specific URL, email attachment hash, or rule set. When a request triggers a rule, the filter logs this CID to identify which policy was applied (e.g., block, allow, quarantine).

Speculation and Possibilities

Security Measure: It could be part of a broader security measure to ensure that data accessed or modified is legitimate and trackable.
Customization and Personalization: Perhaps it's used to tailor user experiences, offering personalized content based on unique interactions or preferences.

2. Context: Why are you seeing this?

You typically encounter this string in one of two scenarios:

Log Analysis: You are reviewing system logs (specifically system.log, debug.log, or traffic logs) and see an entry associating this ID with an allowed or blocked action.
Registry/Database Lookup: You found this key in the Windows Registry or an internal SQLite database used by the security software.

Purpose

This filter is used to match, block, allow, or modify a specific content stream identified by the unique hash 87d25e32ac0d4ef0b1e0502c6b7dfb77.

5. Tuning / False Positives

scfilter can be CPU‑intensive on high‑throughput links – monitor performance with suricata --dump-counters.
If false positives occur, check if the matched content is generic (e.g., common HTML/JS).
Whitelist trusted IPs or adjust the threshold / suppression in Suricata.