4.5b — Web Filtering + OS Security (11 + 7 = 18, combined since OS Security alone is too small to stand as its own set)

Content filter / URL filter / website category filter

Controls what web content users can access, based on URL, category, or content itself.

URI (Uniform Resource Identifier)

Broader term sometimes used interchangeably with URL.

Allow list / block list (URL)

Explicit lists of permitted or forbidden individual URLs.

URL category filtering

Grouping URLs into categories (auction, hacking, malware, travel, recreation, etc.) instead of managing individual domains one by one.

NGFW-integrated URL filtering

URL filtering consolidated into a next-gen firewall, one device managing firewall rules, IPS, and URL filtering together.

Agent-based content filter

Filtering software installed directly on the user's device, enforcing rules regardless of which network they connect to.

Website reputation filtering

Filtering based on an assessed risk score (trustworthy, low risk, medium risk, suspicious, high risk) rather than just category or exact domain.

Automated reputation scanning

Since manual review of every website is impossible at scale, reputation scores are typically generated automatically, with manual override available.

DNS filtering

Blocking malicious or undesirable sites at the DNS resolution level; the DNS server simply refuses to return an IP address for a known-bad domain.

DNS filtering vs malware C2

DNS filtering isn't limited to browser traffic; it can also block malware from resolving its command-and-control server's domain.

Active Directory (AD)

Microsoft's centralized database of network objects: computers, users, file shares, printers, security groups, used to manage authentication and permissions.

Group Policy

Overlay of configuration and security settings applied to users/devices stored in Active Directory; managed via the Group Policy Management Editor.

Discretionary Access Control (DAC)

Access control model where the resource owner or user decides who gets access; Linux's default behavior.

Mandatory Access Control (MAC)

Access control model where a central administrator, not the individual user, assigns all rights and permissions.

SELinux (Security-Enhanced Linux)

A set of kernel patches enabling mandatory access control on Linux, shifting it away from its default discretionary model.

Least privilege (reinforced)

Users and processes get only the access needed for their specific job function, nothing more, limiting the blast radius of a breach.