Survey of Intrusion Detection and Attack Description Languages by qaz91038

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									Survey of Intrusion Detection and Attack
        Description Languages
                Based on
     Monitoring Program Behavior




                          Erbil YILMAZ
                     Area Survey Exam
                         Summer 2003
Intrusion Detection Approaches
 Anomaly Detection
   Detect deviations from normal behavior
 Misuse Detection
   Looks for pattern or predefined sequences of
     events defining a known attack
 Specification Based
   Describes the intended behavior of
     programs
Monitoring Program Behavior
 Regardless of the nature of an attack, damage
  can ultimately be affected only via system calls
  made by processes running on the target
  system
 By monitoring and restricting system calls,
  possible attacks can be prevented
 Increase efficiency of IDS
 System call interception is usually achieved by
  wrappers
Early Systems Using Program
Behavior Patterns
 JANUS
   Restricts access of untrusted helper
    applications to the operating system
 “Sense of Self” for Unix Processes
   Normal behavior is defined by short-range
    correlations in a process’s system calls
 DPEM
   Describes a security-critical application’s
    intended behavior through specifications
JANUS

 Netscape and ghostview example
 Uses “/proc virtual file system”
 Modular approach: framework + dynamic
  policy modules
 First configuration file is read, which contains
  lines like:
    path allow read, write /tmp/*
JANUS Modules
 Basic module: Supplies defaults for system
  calls that are easiest to analyze and takes no
  configuration parameters.
 Putenv module: Allows one to specify
  environment variable settings for the traced
  application via its parameters. The ones that
  are not mentioned are unset.
 Tcpconnect module: Allows restricting TCP
  connections by host and port.
 Path module: Allows or denies path access
  according to patterns.
Sense of Self for Unix Processes

 Based on an analogy between the human
  immune system and intrusion detection
 Normal behavior is defined by short-range
  correlations in a process’s system calls
 Unix’s strace is used to intercept system calls
 A file of short sequences of system calls is
  created
Short Sequence of System Calls
Creation Procedure

 Application runs and all its system calls are
  recorded
 These sequences then decomposed into short
  sequences using sliding window
 Unique ones are stored in a database and
  called N-grams
 Comparatively small collection of short
  sequences derived
DPEM

 Describes a security-critical application’s
  intended behavior through specifications
 Monitors its behavior for violations of these
  specifications also called trace policies
 Audit trails are used to check for violations of
  these trace policies
Security Relevant Characteristics of
Programs
 Access: The set of system objects being
  accessed through the program’s execution.
 Sequencing: The order of operations performed
  by a program.
 Synchronization: Refers to improper
  synchronizations of programs.
 Race Conditions: A special case of the
  synchronization problem.
Example
   1. SPEC <(?, binmail, U, H)>
   2. ENV int CREATTMP = 0;
   3. ENV int PID = getpid();
   4. SE: <binmail> || <other>
   5. <binmail> -> <init> <mktemp> <rest>.
   6. <init> -> <not_mktemp> <init> | Nil.
   7. <rest> -> any_op <rest> | Nil.
   8. <mktemp> -> open_tmpfile-PID { CREATTMP = 1; }.
   9. <not_mktemp> -> not_open_tmpfile-PID
   10. <other> -> <vop, CREATTMP> <other> | Nil.
   11. <vop, 0> -> not_chgtmp.
   12. <vop, 1> -> any_op.
   13. END;
Attack Description and Specification
Languages
 STATL
   Extensible, domain-independent, state-
    transition-based attack description language
 ASL
   Specifies normal and abnormal behaviors of
    a process as logical assertions about an
    application program’s sequence of system
    calls and their argument values
 BMSL
   Monitors incoming network packets
   Also monitors system calls requested by
    executing processes
STATL
Transition Types and Example
 Non-consuming transition
 Consuming transition
 Unwinding transition
ASL

 Supports automatic defensive actions
 Normal and abnormal behaviors of a process as
  logical assertions
   Local correctness assertions:
        execve(f) | f != “usr/ucb/finger” -> exit(-1)
   Non-interference assertions:
    nonatomic(f) in (access(f, mode) .. open(f)->exit(-1))
ASL
BMSL
 Efficient real-time intrusion detection
 Supports temporally related event sequences
Some Related
Software Engineering Concepts
 Threat Model
   A way to introduce security into design
   Helps list vulnerabilities of a software system
   Helps choose appropriate solutions


 Aspect-Oriented Programming
   Isolates different aspects of programming
   Helps ease of comprehension and maintenance
Threat Modeling Process
1.   Brainstorm the known threats to the system.
2.   Rank the threats by decreasing risk.
3.   Choose how to respond to the threats.
4.   Choose techniques to mitigate the threats.
5.   Choose the appropriate technologies from the
     identified techniques.
 STRIDE Threat Model
        Spoofing identity, Tampering with data, Repudiation,
         Information disclosure, Denial of service, Elevation of
         privileges
Aspect Oriented Programming
 Some aspects of a program’s code
   Data Storage
   Security
   Performance
 Components
 Connectors
 Tangling of the code (aspect weavers)
Conclusions
 Monitoring system calls is effective
 Which system call sequence is normal?
 Program behavior spec’s and monitoring system are
  highly coupled
 Integrate software engineering practices to get better
  specifications

 Specifications should be a part of dev. effort
 Automated generation of monitoring system based on
  spec’s

								
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