VISHVESHWARAIAH TECHNOLOGICAL UNIVERSITY S.D.M COLLEGE OF ENGINEERING AND TECHNOLOGY

Transcription

1 VISHVESHWARAIAH TECHNOLOGICAL UNIVERSITY S.D.M COLLEGE OF ENGINEERING AND TECHNOLOGY A seminar report on COMPUTER FORENSICS Submitted by SUJAY P. 2SD06CS110 8 th semester DEPARTMENT OF COMPUTER SCIENCE ENGINEERING

2 VISHVESHWARAIAH TECHNOLOGICAL UNIVERSITY S.D.M COLLEGE OF ENGINEERING AND TECHNOLOGY DEPARTMENT OF COMPUTER SCIENCE ENGINEERING CERTIFICATE Certified that the seminar work entitled COMPUTER FORENSICS Is a bonafide work presented by SUJAY P. baring USN NO 2SD06CS110 in a partial fulfillment for the award of degree of Bachelor of Engineering in computer science of the Vishveshwaraiah Technological University, Belgaum during the year The seminar report has been approved as it satisfies the academic requirements with respect to seminar work presented for the Bachelor of Engineering Degree.Staff in charge Prof S.L DESHPANDE H.O.D Page 2

3 CONTENT Introduction History of Computer Forensics Steps of Computer Forensics Reasons for Evidence Users Computer Forensics Handling Evidence Handling Information Evidence Processing Guidelines Methods of Hiding Data Methods of Detecting/Recovering Data Network forensics Advantages of Computer Forensics Disadvantages of Computer Forensics Conclusion Page 3

4 Introduction Computer forensics is simply the application of disciplined investigative techniques in the automated environment and the search, discovery, and analysis of potential evidence. It is the method used to investigate and analyze data maintained on or retrieved from electronic data storage media for the purposes of presentation in a court of law, civil or administrative proceeding. Evidence may be sought in a wide range of computer crime or misuse cases. Computer forensics is rapidly becoming a science recognized on a par with other forensic sciences by the legal and law enforcement communities. As this trend continues, it will become even more important to handle and examine computer evidence properly. Not every department or organization has the resources to have trained computer forensic specialists on staff. Computer evidence has become a fact of life' for essentially all law enforcement agencies and many are just beginning to explore their options in dealing with this new venue. Almost overnight, personal computers have changed the way the world does business. They have also changed the world s view of evidence because computers are used more and more as tools in the commission of traditional' crimes. Evidence relative to embezzlement, theft, extortion and even murder has been discovered on personal computers. This new technology twist in crime patterns has brought computer evidence to the forefront in law enforcement circles. Forensic science has been defined as any science used for the purposes of the law... [Providing] impartial scientific evidence for use in the courts of law, and in a criminal investigation and trial. According to Marcus Ranum, Network forensics is the capture, recording, and analysis of network events in order to discover the source of security attacks or other problem incidents. Page 4

5 We expand on these definitions to define computer forensics as: Computer forensics involves the preservation, identification, extraction, documentation, and interpretation of computer media for evidentiary and/or root cause analysis. These activities are undertaken in the course of a computer forensic investigation of a perceived or actual attack on computer resources. Evidence might be required for a wide range of computer crimes and misuses. Multiple methods of Discovering data on computer system. Recovering deleted, encrypted, or damaged file information. Monitoring live activity. Detecting violations of corporate policy. Information collected assists in arrests, prosecution, termination of employment, and preventing future illegal activity. What Constitutes Digital Evidence? Any information being subject to human intervention or not, that can be extracted from a computer. Must be in human-readable format or capable of being interpreted by a person with expertise in the subject. Page 5

6 Computer Forensics Examples Recovering thousands of deleted s. Performing investigation post employment termination. Recovering evidence post formatting hard drive. Performing investigation after multiple users had taken over the system. History of Computer Forensics Michael Anderson Father of computer forensics. Special agent with IRS. Meeting in 1988 (Portland, Oregon) Creation of IACIS, the International Association of Computer Investigative Specialists. The first Seized Computer Evidence Recovery Specialists (SCERS) classes held. Page 6

7 Steps of Computer Forensics Computer Forensics is a four (4) step process Acquisition Physically or remotely obtaining possession of the computer, all network mappings from the system, and external physical storage devices. Identification This step involves identifying what data could be recovered and electronically retrieving it by running various Computer Forensic tools and software suites. Evaluation Evaluating the information/data recovered to determine if and how it could be used again the suspect for employment termination or prosecution in court. Presentation This step involves the presentation of evidence discovered in a manner which is understood by lawyers, non-technically staff/management, and suitable as evidence as determined by United States and internal laws. Page 7

8 Computer forensics process Page 8

9 Reasons for Evidence Wide range of computer crimes and misuses Non-Business Environment: evidence collected by Federal, State and local authorities for crimes relating to: Theft of trade secrets Frauda Extortion SPAM investigations Virus/Trojan distribution Homicide investigations Intellectual property breaches Unauthorized use of personal information Forgery Computer related crime and violations include a range of activities including: Business Environment: Theft of or destruction of intellectual property Unauthorized activity Tracking internet browsing habits Reconstructing Events Inferring intentions Selling company bandwidth Software Piracy Page 9

10 Users Computer Forensics Criminal Prosecutors Rely on evidence obtained from a computer to prosecute suspects and use as evidence. Civil Litigations Personal and business data discovered on a computer can be used in fraud, divorce, harassment, or discrimination cases. Insurance Companies Evidence discovered on computer can be used to mollify costs. Private Corporations Obtained evidence from employee computers can be used as evidence in harassment, fraud, and embezzlement cases. Law Enforcement Officials Rely on computer forensics to backup search warrants and post-seizure handling. Individual/Private Citizens Obtain the services of professional computer forensic specialists to support claims of harassment, abuse, or wrongful termination from employment. Page 10

11 Handling Evidence Admissibility of Evidence Legal rules which determine whether potential evidence can be considered by a court. Must be obtained in a manner which ensures the authenticity and validity and that no tampering had taken place. No possible evidence is damaged, destroyed, or otherwise compromised by the procedures used to search the computer. Preventing viruses from being introduced to a computer during the analysis process. Extracted / relevant evidence is properly handled and protected from later mechanical or electromagnetic damage. Establishing and maintaining a continuing chain of custody. Limiting the amount of time business operations are affected. Not divulging and respecting any ethically [and legally] client-attorney information that is inadvertently acquired during a forensic exploration. Page 11

12 Handling Information Information and data being sought after and collected in the investigation must be properly handled. Volatile Information Network Information Communication between system and the network. Active Processes Programs and daemons currently active on the system. Logged-on Users Users/employees currently using system. Open Files Libraries in use; hidden files; Trojans (root kit) loaded in system. Non-Volatile Information This includes information, configuration settings, system files and registry settings that are available after reboot. Accessed through drive mappings from system. This information should investigate and reviewed from a backup copy. Page 12

13 Evidence Processing Guidelines Following are the 16 recommended steps in processing evidence Step 1: Shut down the computer Considerations must be given to volatile information. Prevents remote access to machine and destruction of evidence (manual or antforensic software). Step2: Document the Hardware Configuration of the System. Note everything about the computer configuration prior to re-locating. Step 3: Transport the Computer System to a Secure Location Do not leave the computer unattended unless it is locked in a secure location. Step 4: Make Bit Stream Backups of Hard Disks and Floppy Disks. Step 5: Mathematically Authenticate Data on All Storage Devices Must be able to prove that you did not alter any of the evidence after the computer came into your possession. Step 6: Document the System Date and Time. Step 7: Make a List of Key Search Words. Step 8: Evaluate the Windows Swap File. Step 9: Evaluate File Slack File slack is a data storage area of which most computer users are unaware; a source of significant security leakage. Page 13

14 Step 10: Evaluate Unallocated Space (Erased Files). Step 11: Search Files, File Slack and Unallocated Space for Key Words. Step 12: Document File Names, Dates and Times. Step 13: Identify File, Program and Storage Anomalies. Step 14: Evaluate Program Functionality. Step 15: Document Your Findings. Step 16: Retain Copies of Software Used. Page 14

15 Methods of Hiding Data To human eyes, data usually contains known forms, like images, , sounds, and text. Most Internet data naturally includes gratuitous headers, too. These are media exploited using new controversial logical encodings: steganography and marking. Steganography: The art of storing information in such a way that the existence of the information is hidden. Watermarking: Hiding data within data Information can be hidden in almost any file format. File formats with more room for compression are best Image files (JPEG, GIF) Sound files (MP3, WAV) Video files (MPG, AVI) The hidden information may be encrypted, but not necessarily. Numerous software applications will do this for you: Many are freely available online. Hard Drive/File System manipulation Slack Space is the space between the logical end and the physical end of file and is called the file slack. The logical end of a file comes before the physical end of the cluster in which it is stored. The remaining bytes in the cluster are remnants of previous files or directories stored in that cluster. Slack space can be accessed and written to directly using a hex editor. This does not add any used space information to the drive. Hidden drive space is non-partitioned space in-between partitions Page 15

16 The File Allocation Table (FAT) is modified to remove any reference to the non-partitioned space. The address of the sectors must be known in order to read/write information to them. Bad sectors occur when the OS attempts to read info from a sector unsuccessfully. After a (specified) number of unsuccessful tries, it copies (if possible) the information to another sector and marks (flags) the sector as bad so it is not read from/written to again. users can control the flagging of bad sectors. Flagged sectors can be read to /written from with direct reads and writes using a hex editor. Extra Tracks: most hard disks have more than the rated number of tracks to make up for flaws in manufacturing (to keep from being thrown away because failure to meet minimum number). Usually not required or used, but with direct (hex editor) reads and writes, they can be used to hide/read data. Change file names and extensions i.e. rename a.doc file to a.dll file. Page 16

17 Methods of Detecting/Recovering Data Steganalysis - the art of detecting and decoding hidden data. Hiding information within electronic media requires alterations of the media properties that may introduce some form of degradation or unusual characteristics. The pattern of degradation or the unusual characteristic of a specific type of steganography method is called a signature. Steganalysis software can be trained to look for a signature. Steganalysis Methods - Detection Human Observation Opening a text document in a common word processor may show appended spaces and invisible characters. Images and sound/video clips can be viewed or listened to and distortions may be found. Generally, this only occurs if the amount of data hidden inside the media is too large to be successfully hidden within the media (15% rule). Software analysis Even small amounts of processing can filter out echoes and shadow noise within an audio file to search for hidden information. If the original media file is available, hash values can easily detect modifications. Disk analysis utilities can search the hard drive for hidden tracks/sectors/data. Page 17

18 RAM slack is the space from the end of the file to the end of the containing sector. Before a sector is written to disk, it is stored in a buffer somewhere in RAM. If the buffer is only partially filled with information before being committed to disk, remnants from the end of the buffer will be written to disk. In this way, information that was never "saved" can be found in RAM slack on disk. Firewall/Routing filters can be applied to search for hidden or invalid data in IP datagram headers. Statistical Analysis Most steganographic algorithms that work on images assume that the Least Significant Bit (LSB) is random If a filter is applied to an image, the LSB bits will produce a recognizable image, so the assumption is wrong After inserting hidden information into an image, the LSB is no longer non-random (especially with encrypted data). If you apply the same filter, it will no longer produce a recognizable image Statistical analysis of the LSB will tell you if the LSB bits are random or not Can be applied to audio files as well (using LSB) Frequency scanning Software can search for high, inaudible frequencies. Steganalysis methods Recovery Recovery of watermarked data is extremely hard. Currently, there are very few methods to recover hidden, encrypted data. Page 18

19 Data hidden on disk is much easier to find. Once found, if unencrypted, it is already recovered Deleted data can be reconstructed (even on hard drives that have been magnetically wiped) Check swap files for passwords and encryption keys which are stored in the clear (unencrypted) Software Tools Scan for and reconstruct deleted data Break encryption Example: GetFree - Forensic Data Capture Tool When files are 'deleted' in DOS, Windows, Windows 95 and Windows 98, the data associated with the file is not actually eliminated. It is simply reassigned to unallocated storage space where it may eventually be overwritten by the creation of new files over time. Such data can provide the computer forensics investigator with valuable leads and evidence. GetSlack - Forensic Data Capture Utility this software is used to capture all of the file slack contained on a logical hard disk drive or floppy diskette on a DOS, Windows, Windows 95 and/or Windows 98 computer system. The resulting output from GetSlack can be analyzed with standard computer utilities or with special NTI tools, e.g., Filter_I and Net Threat Analyzer software. Forensic Graphics File Extractor - NTI's Forensic Graphics Image File Extractor is a computer forensics software tool which was designed to automatically extract exact copies of graphics file images from ambient data sources and from SafeBack bit stream image backup files. The latter process has the potential of quickly identifying all graphics file images stored Page 19

20 on a computers hard disk drive. The resulting output image files can be quickly evaluated using a graphics file viewer. DiskScrub - Hard Drive Data Elimination Software It is becoming standard practice in corporations, government agencies, law firms and accounting firms to reassign computers and to donate older computers to charity. Millions of personal computers have been put to use since 1981 when the IBM Personal Computer came into existence. Many of the older personal computers have been reassigned or donated to charity and many more will fall into this category in the future. However, data security is often ignored when computers change hands. You must be aware that personal computers were never designed with security in mind. Potentially anything that transpired on a used computer still exists. Multiply that by the number of computers your organization will reassign or surplus this year, and you get the point. Computers should be reassigned and donated to charity but the contents of the hard disk drives should not be ignored. With computer technology changing almost daily, corporations and government agencies have to stay current while still making the best uses of aging computer resources. Advancements in hard disk drive storage capacities, operating systems and software applications cause corporations to buy or lease new computers every year. But what is done with the old computers? What is done about the sensitive data still Existing, essentially "stored" on these computers when they are sold, transferred or donated? That is a serious problem, and NTI's Disk Scrub software was specifically designed to deal with these risks, for corporations, government agencies, hospitals, financial institutions, law firms and accounting firms. Page 20

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22 Network forensics As technology has advanced, computers have become incredibly powerful. Unfortunately, as computers get more sophisticated, so do the crimes committed with them. Distributed Denial of Service Attacks, ILOVEYOU and other viruses, Domain Name Hijacking, Trojan Horses, and Websites shut down are just a few of the hundreds of documented attack types generated by computers against other computers usually using an electronic network. The need for security measures to prevent malicious attacks is well recognized and is a fertile research area as well as a promising practioner's marketplace. Though there is an immense effort ongoing to secure computer systems and prevent attacks, it is clear that computer and network attacks will continue to be successful. When attacks are successful, forensics techniques are needed to catch and punish the perpetrators, as well as to allow recovery of property and/or revenue lost in the attack. Computer and Network Forensics (CNF) techniques are used to discover evidence in a variety of crimes ranging from theft of trade secrets, to protection of intellectual property, to general misuse of computers. The ultimate goal of computer and network forensics is to provide sufficient evidence to allow the criminal perpetrator to be successfully prosecuted. As such, CNF efforts are mainly centered in law enforcement agencies. Any enterprise that depends on, or utilizes, computers and networks should have a balanced concern for security and forensic capabilities. Unfortunately, there is little academic or industrial research literature available on CNF. Forensic techniques are developed by the try and fix method, and few organizations have plans for conducting forensics in response to successful attacks. We propose several categories of policies that will help enterprises deter computer crime and will position them to respond effectively to successful attacks by improving their ability to conduct computer and network forensics. These policies correlate to taxonomy of approaches common to computer attacks. We present policies in the following categories: Retaining Information, Planning the Response, Training, Accelerating the Investigation, Preventing Anonymous Activities and Protecting the Evidence. The evidence found during a forensic investigation may depend on the type of crime committed. For example, in a criminal case, incriminating evidence may be found such as documents related to homicides, financial fraud, drug or embezzlement record keeping, or Page 22

23 child pornography. In a civil case, evidence of personal and business records related to fraud, divorce, discrimination, or harassment could be found. CNF experts are not only hired by lawyers. CNF techniques are sometimes needed by insurance companies to discover evidence to decrease the amount paid in an insurance claim. Individuals may also hire CNF experts to support a claim of wrongful termination, sexual harassment, or discrimination. Gathering evidence is at the heart of CNF. In computer-related crimes, evidence is accumulated from information collected by different components of the system. The information does not become evidence until a crime is committed and this data is used to find clues. For this reason, we call the data collected by the system potential evidence. There are many sources of potential evidence in computers and network components. Files are an obvious source of potential evidence. Application output word processors, spread sheets, etc. are almost always valuable potential evidence, as are hidden application files that may contain history information, caches, backups, or activity logs. Occasionally, sophisticated criminals may encrypt incriminating files or attempt to hide them with system-oriented or otherwise unlikely looking names. There are numerous sources of potential evidence, which we discuss more exhaustingly in the section dedicated to establishing recommended policies. Because gathering potential evidence may not be as easy as finding application files on a computer, it requires someone with special skills. CNF experts are specially trained with the skills necessary to successfully carry out a forensic investigation. A forensics expert must have the investigative skills of a detective, the legal skills of a lawyer, and the computing skills of the criminal. Even with these skills, CNF is not an exact science, so there is no guarantee that an expert will find sufficient evidence. However, experienced forensics specialists can find more potential evidence than even the best hackers will expect. Page 23

24 Advantages of Computer Forensics It has an ability to search through a massive amount of data Quickly Easily Thoroughly In any language Disadvantages of Computer Forensics Digital evidence accepted into court Must prove that there is no tampering. All evidence must be fully accounted for. Computer forensic specialists must have complete knowledge of legal requirements, evidence handling and storage and documentation procedures Costs. Producing electronic records & preserving them is extremely costly. Presents the potential for exposing privileged documents. Legal practitioners must have extensive computer knowledge. Page 24

25 Conclusion Practical investigations tend to rely on multiple streams of evidence which corroborate each other - each stream may have its weaknesses, but taken together may point to a single conclusion. Disk forensics may remain for some time the single most important form of digital evidence.increasing number of computer crime means increasing demand for computer forensics services. In doing computer forensics investigation, choosing the right disk imaging tool is very important. There is no standard conformity of computer forensic imaging methodology or tool. This paper only provides guidance and suggestions regarding imaging tool. It should not be constructed as mandatory requirement. Today, everyone is exposed to potential attacks and has a responsibility to its network neighbors to minimize their own vulnerabilities in an effort to provide a more secure and stable network. As the enormity of the problem unfolds, we will better comprehend how vital it is to work towards dramatic changes in research, prevention, detection and reporting, and computer crime investigation. Security can no longer be thought of as an impediment to accomplishing the mission, but rather a basic requirement that is properly resourced. Our focus has been to implement the newest and most advanced technology, but little has prepared us for the gaping security holes we ve neglected to mend along the way. From the ranks of management to every employee that works behind each terminal, the policies that protect and mitigate risks must be current, understood, and aggressively enforced. Reporting must be standard operating procedure so that everyone can realize the total impact and define what is required for a secure cyber environment. The responsibility belongs to everyone and it is with that effort we will be able to harness the security of this new technological age. An enormous challenge lies before us and we must attack it with the same enthusiasm and determination that brought us to this new frontier. Page 25

26 References All State Investigations, Inc. January tateinvestigation.com/computerforensicservices.htm Computer Forensics, Inc. Computer Forensic Services, LLC. January International Association of Computer Investigative Specialists. January Middlesex County Computer Technology. January Virtue, Emily. Computer Forensics: Implications for Litigation and Dispute Resolutions. April df Page 26