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Social Engineering
Tricking user to assist in the comprise of their own systems or personal information Spam e-mail
Most spam is sent by botnets using compromised user systems
Advertising, scams, carrier of malware (attachment), or phishing attack
Trojan horse program A useful, or apparently useful program or utility
containing hidden code that performs some unwanted or harmful funciton
Social Engineering
Trojan horse program E.g. claim to be antivirus scanner, security update
actual carrying payload such as spyware Three models of Trojan horses
Continuing to perform the function of the original program and additionally performing a separate malicious activity
… but modifying the function to perform malicious activity
Performing a malicious function that completely replaces the function of the original program
Malware Payload
System corruption Data destruction Ransomware, e.g. Gpcode Trojan Real-world damage: cause damage to physical
equipment Logic bomb: is set to “explode” when certain
conditions are met
Malware Payload
Attack agent Bot: malware subverts the computational and
network resources of infected system for use by the attacker
The uses of bots: DDoS attack, Spamming … Botnet: the collection of bots often is capable of
acting in a coordinated manner.
Malware Payload Information theft
Keyloggers and Spyware What is a keylogger? (next slide)
Countermeasure to keylogger Spyware
Phishing and Identity theft URL of fake Web site controlled by the attacker Spear-phishing: an email claiming to be from a trusted
sources, the recipients are carefully researched by the attacker greatly increases the likehood of the recipient responding as desired by the attacker
Malware Payload
Backdoor and Rootkit Backdoor (trapdoor) is a secret entry point into a
program without going through the usual security access procedures
Rootkit is a set of programs installed on a system to maintain covert access to that system with root privileges, while hiding evidence of its presence Make many changes to a system to hide its existence Difficult to detect
Keyloggers Keyloggers are used to capture
keystrokes on a computer Hardware Software
Software Behaves like Trojan programs
Hardware Easy to install Goes between the keyboard and the
CPU KeyKatcher and KeyGhost
Countermeasures of malware
Ensure all systems are current All patches applied
Set appropriate access controls on the applications and data to reduce the number of files that any user can
access Training the users to against social
engineering attack
Countermeasures of malware
Technical mechanism to mitigate threat Detection Identification Removal
Requirements for effective malware countermeasures Generality, Timeliness, Resiliency, minimal DOS costs,
transparency, global and local coverage
Countermeasures of malware
Four generations of antivirus software 1st generation 2nd generation 3rd generation 4th generation
More sophisticated antivirus approaches Host-based behavior-blocking Perimeter scanning approaches
(Reading page 323 – 327)
Distributed Denial-of-Service (DDoS) Attacks
DDoS attack on a host from multiple servers or workstations
Network could be flooded with billions of requests Loss of bandwidth Degradation or loss of speed
Often participants (zombies) are not aware they are part of the attack Thousands zombies are controlled by the attacker via
Trojan programs
DDoS Tools and Countermeasures
DDoS countermeasures: • Security patches from software vendors• Antivirus software• Firewalls: Ingress (inbound) and egress (outbound) filtering
(details next …)
Buffer Overflow Attacks A vulnerability in poorly written code
does not check predefined size of input field
Goal of buffer overflow attack: Fill overflow buffer with executable code OS executes this code, elevates attacker’s permission
Administrator Owner of running application
To stop software exploits Train your programmer in developing applications with security in
mind Stay appraised of latest security patches provided by software
vendors
Buffer Overflow Exploits
Buffer Overflow Exploits is the Most common cause of Internet attacks
Over 50% of advisories published by CERT (computer security incident report team) are caused by various buffer overflows
Morris worm (1988): overflow in fingerdInfected 10% of the existing Internet
CodeRed (2001): overflow in MS-IIS server300,000 machines infected in 14 hours
SQL Slammer (2003): overflow in MS-SQL server75,000 machines infected in 10 minutes
Buffer is a data storage area inside computer memory (stack or heap) Intended to hold pre-defined amount of data
If more data is stuffed into it, it spills into adjacent memory
If executable code is supplied as “data”, victim’s machine may be fooled into executing it Code will self-propagate or give attacker control over
machine
Attack can exploit any memory operation Pointer assignment, format strings, memory allocation
and de-allocation, function pointers, calls to library routines via offset tables
Memory Buffers
Stack Buffers
Suppose Web server contains this functionvoid func(char *str) {
char buf[126]; strcpy(buf,str); }
When this function is invoked, a new frame with local variables is pushed onto the stack
Allocate local buffer(126 bytes reserved on stack)
Copy argument into local buffer
Top ofstack
Stack grows this way
buf sfpret
addr str
Local variables Pointer toprevious
frame
Frame of thecalling function
Execute code at
this address after func()
finishes
Arguments
What If Buffer is Overstuffed? Memory pointed to by str is copied onto stack…
void func(char *str) { char buf[126]; strcpy(buf,str); }
If a string longer than 126 bytes is copied into buffer, it will overwrite adjacent stack locations
strcpy does NOT check whether the string at *str contains fewer than 126 characters
Top ofstack
buf strFrame of thecalling function
This will beinterpreted
as return address!
overflow
Executing Attack Code
Suppose buffer contains attacker supplied string For example, *str contains a string received from the network as
input to some network service daemon
When function exits, code in the buffer will be executed, giving attacker a shell
The attacker gets a root shell if the victim program is SUID root
Top ofstack
code strFrame of thecalling function ret
Attacker puts actualinstructions into his input string, e.g.,
binary code of execve(“/bin/sh”)
In the overflow, a pointer backinto the buffer appears in
the location where the systemexpects to find return address
Executable attack code is stored on stack, inside the buffer containing attacker’s string Stack memory is supposed to contain only data, but…
Overflow portion of the buffer must contain correct address of attack code in the RET position The value in the RET position must point to the beginning
of attack code in the buffer Otherwise application will crash with segmentation
violation Attacker must know or correctly guess in which stack
position his buffer will be when the function is called
Some Issues on Buffer Overflow
The Cause : No Range Checking strcpy does not check input size
strcpy(buf, str) simply copies memory contents into buf starting from *str until “\0” is encountered
Ignoring the size of area allocated to buf
Many C library functions are unsafe strcpy(char *dest, const char *src) strcat(char *dest, const char *src) gets(char *s) scanf(const char *format, …) printf(const char *format, …)
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