What does HIDS stand for?
HIDS stands for Host-based Intrusion Detection System. Software on a single host that detects intrusions by watching its logs, files and processes, and alerts without blocking.
A HIDS is software installed on one computer that watches what happens on that computer: log entries, changes to important files, running processes, sign-ins and configuration changes. Because it sits on the host, it sees activity after the traffic has been decrypted and it sees things that never cross the network, such as a local user changing a system file. Its limit is the same fact: it only knows about the machine it runs on, and an attacker with administrator rights may try to switch it off.
HIDS in practice: an example
A web server runs a HIDS agent with file integrity monitoring. At night a file in the web root changes although no deployment was scheduled. The agent compares the file with its stored hash, sees the difference and sends an alert to the SIEM with the file path and the account that made the change.
What HIDS is confused with
HIDS vs NIDS: what is the difference?
A HIDS watches one host from the inside: files, logs and processes. A NIDS watches the traffic of a network segment from the outside. Most organizations use both, because each sees what the other cannot. What NIDS stands for
HIDS vs HIPS: what is the difference?
A host-based intrusion prevention system can block the action, for example by stopping the process. A HIDS only detects and reports.
Which exams cover HIDS?
HIDS is on the official CompTIA acronym list for one of the four exams covered here.
- Security+ SY0-801: 4.1 (Security Operations).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. An attack arrives inside an encrypted HTTPS session and modifies a configuration file on the server. Which control is best placed to detect the modification?
- A NIDS on a mirrored switch port
- A HIDS with file integrity monitoring
- A cable tester
- A DHCP reservation
Show the answer
B. A HIDS with file integrity monitoring. The network sensor only sees encrypted traffic. The host agent sees the file change itself, after decryption, and can compare the file with a known-good hash.
2. Which is a limitation of a HIDS?
- It cannot read local log files
- It needs a mirrored port on the switch
- It only sees activity on the host where it is installed
- It cannot work on servers
Show the answer
C. It only sees activity on the host where it is installed. A host agent has no view of other machines or of traffic that never reaches its host, which is why it is paired with network sensors and central log collection.
Sources: NIST SP 800-94, Guide to Intrusion Detection and Prevention Systems; NIST glossary: HIDS. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.