Download Computer Systems Security

Computer Systems Security
Part I
ET4085 Keamanan Jaringan Telekomunikasi
Tutun Juhana
School of Electrical Engineering and Informatics
Institut Teknologi Bandung
Computer systems security is all
about the security threats that can
compromise an operating system
and the data held within
Threats: viruses, Trojans, and spyware are
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COMPUTER SYSTEMS SECURITY
THREATS
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Malicious Software
• Malicious software, or malware, is software
designed to infiltrate a computer system and
possibly damage it without the user’s knowledge
or consent
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Viruses
Worms
Trojan horses
Spyware
Rootkits
Adware
and other types of undesirable software.
Viruses
• A virus is code that runs on a computer without the
user’s knowledge; it infects the computer when the
code is accessed and executed
• For viruses to do their dirty work, they first need to be
executed by the user in some way
– A virus needs some sort of carrier
• A virus also has reproductive capability and can spread
copies of itself throughout the computer if it is first
executed by the user
• By infecting files accessed by other computers, the
virus can spread to those other systems as well
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• Viruses types
– Boot sector - Initially loads into the first sector of
the hard drive; when the computer boots, the
virus then loads into memory.
– Macro - Usually placed in documents and e-mailed
to users in the hopes that the user will open the
document, thus executing the virus.
– Program - Infects executable files
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• Viruses types (2)
– Polymorphic - Can change every time is it executed in an
attempt to avoid antivirus detection.
– Stealth - Uses various techniques to go unnoticed by
antivirus programs.
– Armored - These protect themselves from antivirus
programs by tricking the program into thinking that it is
located in a different place from where it actually resides
• Essentially, it has a layer of protection that it can use against the
person who tries to analyze it; it will thwart attempts by analysts
to examine its code.
– Multipartite - A hybrid of boot and program viruses that
attacks the boot sector or system files first and then
attacks the other
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Worms
• Worms are much like viruses
except they self-replicate whereas
a virus does not
• With worms, the user doesn’t
need to access and execute the
malware
• Worms take advantage of
backdoors and security holes in
operating systems and
applications
– They look for other systems on the
network or through the Internet
that are running the same
applications and replicate to those
other systems
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Trojan Horses
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• Trojan horses, or simply Trojans, appear to
perform wanted functions but are actually
performing malicious functions behind the
scenes
• These are not technically viruses and can
easily be downloaded without noticing them
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• Remote access Trojans (RATs)
are the most common type of
Trojan (ex: Back Orifice or
NetBus)
– their capability to allow an
attacker higher administration
privileges than the owner
• When a target computer is
controlled by an attacker, it
could easily become a robot (or
simply a bot), carrying out the
plans of the attackers at their
command
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Spyware
• Spyware is a type of malicious software either
downloaded unwittingly from a website or
installed along with some other third-party
software
• Usually, this malware collects information about
the user without the user’s consent.
• Spyware is also associated with advertising (those
pop-ups that just won’t go away!) and could
possibly change the computer configuration
– Adware usually falls into the realm of spyware
because it pops up advertisements based on what
it has learned from spying on the user
• Grayware is another general term that describes
applications that are behaving improperly but
without serious consequences
– It is associated with spyware, adware, and joke
programs
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Rootkits
• A rootkit is a type of software designed to gain
administrator-level control over a computer
system without being detected
– The term is a combination of the words “root”
(meaning the root user in a UNIX/Linux system or
administrator in a Windows system) and “kit”
(meaning software kit)
– Usually, the purpose is to perform malicious
operations on a target computer at a later date
without the knowledge of the administrators or users
of that computer
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• Rootkits are difficult to detect because they
are activated before the operating system has
fully booted
• A rootkit might install hidden files, processes,
and hidden user accounts.
• Because rootkits can be installed in hardware
or software, they can intercept data from
network connections, keyboards, and so on
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• Rootkits can target the BIOS, boot loader,
kernel, and more
• Example: Evil Maid
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Spam
• Spam is the abuse of electronic
messaging systems such as e-mail,
broadcast media, instant messaging,
and so on
• Spammers send unsolicited bulk
messages indiscriminately, usually
without benefit to the actual
spammer, because the majority of
spam is either deflected or ignored
• The bulk of network-based viruses
are transferred through spam emails
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Summary of Malware Threats
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WAYS TO
DELIVER MALICIOUS SOFTWARE
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• Malware is not sentient
(...not yet) and can’t just
appear out of thin air
• it needs to be
transported and
delivered to a computer
or installed on a
computer system in
some manner
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– Direct physical access
– Via Software, Messaging, and Media
– Active Interception
– Privilege Escalation
– Backdoors
– Logic Bombs
– Botnets and Zombies
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Direct physical access
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Via Software, Messaging, and Media
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Active Interception (inception)
the act of exploiting a bug or design flaw in a
software or firmware application to gain access
to resources that normally would’ve been
protected from an application or user
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Privilege Escalation
Backdoors are used in computer programs to bypass normal authentication and
other security mechanisms in place
Originally, backdoors were used by developers as a legitimate way of accessing an
application, but soon after they were implemented by attackers who would use
backdoors to make changes to operating systems, websites, and network devices
Quite often, it is installed via a Trojan horse
Example: Back Orifice (completely new application that would act as a backdoor), which
enables a user to control a Windows computer from a remote location.
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Backdoors
Logic bombs are code that has, in some way, been inserted into software to initiate
one of many types of malicious functions when specific criteria are met
malware delivery system
malware
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Logic Bombs
malware can be distributed throughout the Internet by a group of compromised
computers known as a botnet (controlled by a master computer (where the attacker
resides))
The individual compromised computers in the botnet are called zombies
Leads to
distributed
denial of service
(DDoS)
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Botnets and Zombies
Columbo is an American detective mystery television film series, starring
Peter Falk as Columbo, a homicide detective with the LAPD (wikipedia)
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