Dictionary of Computer Security Terms
When browsing the Emsi Software web pages you may encounter terms that need further
explanation. These terms are explained in the following short reference. All terms
with hyperlinks have a more detailed article available.
- Adware
Adware describes programs that contain advertisements, for example banners. This
is often used to finance development costs. In general, Adware has a poor reputation
because some programs do not adequately mention the presence of advertising or are
too intrusive. Adware modules that constantly download new advertising data can
also create user profiles by monitoring user activity on the PC and thus endanger
your data privacy.
- Backdoor
A "Backdoor" means exactly what it says, an alternative entry point to your computer.
Programmers intentionally build Backdoors into supposedly useful programs to allow
access via the "back door" to the computer where they are installed. This allows
an infected PC to be completely remotely controlled, e.g. for sending Spam.
- Badware
Describes software exhibiting deceptive behavior and which is difficult to remove
or exhibits undesired behavior. See "Malware".
- Behavior Blocker
In contrast to signature-based scanners, Behavior Blockers do not use signatures
and heuristics to recognize damaging software but rather the behavior of the software.
- Botnet
A Botnet describes a large network of computers infected with a particular Trojan.
The author of the Trojan controls the infected computers, which then behave quasi-automatically
like robots. Larger Botnets can consist of thousands of PCs – all unknown to their
owners.
- Buffer Overflow
So-called "buffer overflows" represent the most common security holes in programs
and operating systems. They occur when too much data is loaded into a particular
storage area intended for a smaller amount of data, which can cause errors or crashes.
In the worst case, an attacker can use this to obtain control over another PC. The
most important protection measures are regular software updates.
- Captcha
Is used to decide whether a program or online service is being operated by a human
or machine user. The most common form of Captchas are randomly generated images
containing codes that are to be manually entered. A machine cannot decode the intentionally
distorted letters and numbers. This ensures that (e.g.) a program cannot be switched
off by another program or a Bot.
- Cookie
This is a small snippet of information sent from a web server to a user's browser,
which then stores it. On subsequent access to the same web server this server can
then read back this information snippet and use it to "recognize" the user. This
method is ideally suited to recording user profiles (what was clicked?).
- Dialer
Dialers are a particular type of Malware that dial expensive telephone service numbers
without permission. In the days when Internet access occurred mainly via Modems
and ISDN connections Dialers represented a great danger in the form of horrendous
telephone bills. In the days of DSL they have become less common because DSL does
not use a simple dial-up connection.
- Exploit
An Exploit is the technical term for a damaging program that exploits specific weak
points in a piece of software (for example Buffer Overflows). Attackers can gain
control of an attacked computer via weak points in the operating system or applications.
- False positive
A false positive is a term applied to a failure in an alerting system - most commonly
in an anti-malware product or intrusion detection system. It can occur when file layouts
or behavior patterns of good and bad software are similar. Once reported, false
alerts are usually quickly fixed by the software authors.
- Heuristic
This describes the mathematical analysis of scanned files on the hard drive. The
program code is used to perform a probability calculation of damaging actions.
- Hoax
Describes an intentionally distributed false warning that is treated as true and
passed on by many users. A well-known hoax told users to delete supposedly Malware
files such as SULFNBK.EXE and JDBGMGR.EXE, despite the fact that these are important
system files.
- Guard
This means exactly what it says. Guards are programs or program elements that have
a protective role, meaning that they protect the computer or parts of the computer
from particular attacks.
- HIPS/IDS
The abbreviations HIPS and IDS stand for "Host (based) Intrusion Prevention System"
and "Intrusion Detection System". These are programs or program elements that detect
and prevent the execution of damaging code. Their main advantage is signature-free
recognition, which allows detection of new Exploits and Zero-day attacks for which
no signatures currently exist.
- Keylogger
Keyloggers are small programs invisibly installed on a computer that record all
keyboard input. An attacker can use this to (e.g.) record passwords.
- Malware
The word Malware is composed from the words "malicious" and "software". This is
a collective term for all types of damaging software such as Trojans, Spyware or
Viruses.
- Phishing
Attackers use forged websites to obtain secret passwords. The term comes from "Password
Fishing". The Internet addresses are disguised so that they are almost identical
to the originals. This mainly affects online banking access.
- POC/Proof Of Concept
A "Proof of Concept" is the prototype of a new attack that usually does not contain
distribution routines. When a programmer discovers a new hole in a program (see
Exploit) then they provide evidence of this with a POC. Proofs of Concept are also
created by hackers for negative reasons, but also by employees of security companies
and private programmers.
- Riskware
Riskware comes from the words "risk" and "ware". Simply put, this is software whose
installation presents a possible but not definite risk for the PC.
- Rootkit
Rootkits currently represent the greatest threat to PC users. They install themselves
invisibly on a target system and give the attacker full control over the system.
Once installed, clever hiding mechanisms make Rootkits very difficult or even impossible
to detect. If you detect a Rootkit installation, then a new installation of the
operating system is usually unavoidable because you can no longer trust the PC.
- Scanner
Alongside the hardware of the same name used for digitizing pictures, the term Scanner
also describes a program used for searching a computer. Malware scanners use signatures
and heuristics to detect damaging software.
- Security hole
An attacker can use a security hole to gain access to a PC and install their own
software. See "Exploit". Regular software updates and a Behavior Blocker are useful
against security holes.
- Signature
A signature represents the unique fingerprint of a program. Signatures are especially
used by scanners for recognizing damaging software. Their major disadvantage is
the exponential growth of the number of different versions of damaging software
and the fact that a particular piece of Malware must first be known before a signature
can be created.
- Spyware
Spyware is software that literally spies on the activities of the user of the computer
where it is installed. All possible personal data is gathered and then sent to the
author of the Spyware.
- Trojan
This term comes from the Trojan Horse in Greek mythology. The user thinks that he
or she is installing a useful program such as (e.g.) a small game on his or her
computer. However, Malware is concealed behind the useful program, which is then
also installed on the PC and gives the attacker control over the system.
- Virus
Viruses are the oldest form of damaging software and these are sadly still a current
threat. In contrast to all other types of Malware, a Virus infects a normal program
by injecting its own code into the normal program (comparable to a biological virus
that injects its own genetic information into a human cell). Once run, the virus
attempts to distribute copies of itself and can cause damage in a wide range of
possible ways. A Virus usually requires a "host" and cannot run alone.
- Vulnerability
See "Security hole" and "Exploit".
- Worm
A Worm uses higher-level applications such as a network or email system to distribute
copies of itself in an uncontrolled manner. A Worm can contain damaging routines
but this is not absolutely necessary. A typical distribution path is (e.g.) via
email attachments. When the user opens the attachment, this is automatically sent
to all recipients in the address book.
- Zero-Day Attack
A Zero-Day Attack describes Malware on the first day of distribution. New Malware
is especially dangerous in the first few days because it usually takes a while for
the anti-virus companies to obtain a sample and create a suitable signature. So-called
Behavior Blockers offer better protection here.
- Zombie Computer
A computer infected with a Backdoor Trojan that listens for remote commands and
carries out remotely controlled actions.
5/1/2008
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