Introduction

In the past few decades, the use of computers and internet use has been on the rise. There are more than 2.5 billion internet users worldwide. [1] [2] There are more and more people using social media today. There is also a rise in “Internet of Things” devices, which are home appliances that connect to the internet, such as a thermostat. [3] Crimes involving technology are also on the rise.

Digital forensics or cyber forensics is a relatively new forensic science field that has been solving issues related to the use of technology in crime. Digital forensics experts commonly deal with child pornography, corporate espionage, and copyright infringement.[4]  There are digital forensic journals, and conferences. Digital forensic experts exist in academia, military, law enforcement, and intelligence agencies. It’s a very broad field, and it’s becoming more relevant to the crimes committed these days. It is important for the criminal justice system to keep up with the changes. This paper will discuss history of digital forensics, evidence gathering and processing techniques, problems with digital forensics, and most importantly, the law and how it relates to digital forensics.

History

Florida is the first state that passed the laws regarding computer crimes. In 1978, Florida passed Florida Computer Crimes Act. [5] This act addressed the fact that computer related crimes were on the rise, and it caused harmed to government, as well as the private sector. The act focused on offenses committed against Intellectual property, computer equipment or supplies, and computer users. Offenses against intellectual property included unauthorized modification, destruction, and disclosure of someone else’s computer system or network. The act also counted modification of computer equipment or supply as an offense. Finally, the act counts accessing anyone else’s computer, or conducting denial of service as an offense. The offenses had to be committed willfully and knowingly. Penalties for offenses ranged from misdemeanor to second degree felony. [6] With the increase of computer crimes, the Congress passed Computer Fraud and Abuse Act in 1986.

Computer Fraud and Abuse Act mainly focused on punishing unauthorized access. CFAA criminalized unauthorized access of national security information, and exceeding authorized access.  For example, someone hacking into IUPUI financial computer to get financial information would be punished, and someone who works in the financial department exceeding their privilege to get information would also be punished. Accessing government computers, such as computers owned by a government department or an agency is also punishable. CFAA also dealt with malicious code, computer attacks, and password theft. Transmission of code, program, or command that damaged a protected computer was punishable. Knowingly transmitting computer viruses that are designed to cause damage would fit under this. Protected computer is defined as a computer that is used by a financial institution or US government and computer used for interstate or foreign commerce or communication, including computers outside of US. [7] After CFAA was passed, FBI had the authority to conduct computer crime investigations. FBI, in 1992, created a special team called Computer Analysis and Response Team for digital forensics. CART collected and investigated digital evidence. [8] CART also provides training to digital forensics experts.  

Digital Forensics

CART and forensics department in other agencies most likely had standard operating procedures for dealing with the evidence collection and examination. In 1998, the Scientific Working Group on Digital Forensics was formed. SWGDE was formed to allow communication and cooperation between people who worked in digital forensics. SWGDE also publishes papers on best practices for digital evidence collection and examination [9]

Collection of digital evidence is a bit more complicated than it is in other forensic fields. First challenge is finding the storage devices. With advances in technology, large amount of data can be stored in a small device. Finding these storage devices can be fairly difficult because storage devices can be disguised to look like unsuspicious things, such as pens or flash lights. Second challenge is posed by how a computer fundamentally works. Computer has storage memory (harddrive) and temporary storage memory (RAM). The challenging part of collection is when the computer is turned on. When a computer is turned on and is being used, it puts data into the RAM, which is temporarily there. As soon as the computer is turned off, all the temporary data, which could be evidence, permanently goes away.  [10]

When computer is off, the examiner collects data by cloning the harddrive or the storage device. Examiner attaches the storage device to a write-blocker and attaches the write-blocker to the collection device. Write-blockers prevent data contamination by blocking the examiner or the collection device from writing to the storage device. After the drive is cloned, the examiner has to check the integrity of the clone. Integrity is usually checked by using two or more checksum algorithms. Checksum algorithms generate an alphanumeric string such as “eb61eead90e3b899c6bcbe27ac581660.” The alphanumeric string generated is comparable to DNA; it’s unique to that data. The examiner runs the checksum algorithm on the clone and the suspect’s harddrive to check if they both match. If the checksums match, then the data was not contaminated. [11] Examiners usually create another clone of the original clone to work with.

Harddrive clone is first automatically examined by existing tools, such as Forensic Toolkit and EnCase. These tools automatically recover deleted files, and separate different data for the examiner. Examiner can usually search the harddrive for specific words or filetypes (such as videos or pictures) that are relevant to the case. Examining the evidence this way usually is very time consuming. Depending on the case, examiners use a different method that is less involved. Hashing algorithms discussed earlier can also be applied to individual files, and not just a whole harddrive.

Since the algorithms can be applied to files, the examiner is able to build a database of unique hash values. This is just like Automated Fingerprint Identification System (AFIS) or National Integrated Ballistic Identification Network (NIBIN). An examiner typically uses whitelist of hash values to identify known or good files. The software runs the algorithm on each individual file and compares the results with this whitelist. If the hash value is in the whitelist, the file is known and good. An examiner can also create a database or a list of known bad files, such as child pornography or confidential files.[12] The examining software can apply the algorithm to all the individual files, and if hash value of a file matches with the bad list, the software can alert the examiner. This method allows examiner to quickly identify known bad files or the files they are looking for.

Since digital forensics includes many sub-disciplines, examination method covered in this paper isn’t used by all of them. Examination method covered in this paper is used for most of the cases that law enforcement handles.

Rules, exceptions, and case laws

4th amendment

In most cases, 4th amendment and exceptions to the 4th amendment apply to digital evidence. For example, the person collecting evidence needs to have a warrant to take or search the evidence. The warrant should also include scope of the search. An investigator can get a warrant to search a laptop, but cannot come in and start searching other computers. The investigator may also have to specify the part of laptop they want to search. For example, computer can have multiple folders that are used for storage. An investigator, who gets warrant to search a specific user’s folder, cannot start searching irrelevant folders for evidence. Evidence an investigator searches for has to be related to probable cause. If investigator is looking for evidence of child porn, they cannot start searching for evidence of digital piracy.

Sometimes computers are shared between multiple users. 4th amendment still applies here. One of the users can consent to the search, but the investigator still has to ignore searching folder of another user if they have taken measures to protect it. A user can implement access control to their folders or use password-protected login. The user still has reasonable expectation of privacy. If a user decides to share their folder via peer-to-peer share or a Windows share, they no longer have reasonable expectation of privacy.

Border search exception

Another important rule that applies to computer search and seizer is the border search exception. Border search exception is not really an exception to the 4th amendment. Border search exception rule is to protect country and its people from external threats. The authorities need probable cause to search your devices if you are in the United States. If you are coming into the United States, the authorities have the right to search your devices without any reason or warrant, even if you are a citizen. This rule has been used multiple times to search electronic devices.[13] [14]

Admissibility

The best evidence rule also applies to digital evidence. Best evidence rule (Federal rules of Evidence 1002) states “An original writing, recording, or photograph is required in order to prove its content unless these rules or a federal statute provides otherwise.” This rule is to limit the testimony or description of the evidence, and allow introduction of the original evidence. This rule applies to digital evidence because of the fact that writings, recordings, and photographs can be now stored on a computer or any other digital device. Another rule, Rule 1003, also applies to digital evidence because of the way it’s collected and processed. Rule 1003 states “A duplicate is admissible to the same extent as the original unless a genuine question is raised about the original’s authenticity or the circumstances make it unfair to admit the duplicate.” The digital forensic examiner usually makes at least two duplicates of the original evidence, and according to this rule, it is admissible, just as long as it was authenticated via a hashing algorithm. [15]

Rule 803, titled Exceptions to the Rule Against Hearsay, also applies to digital evidence. Courts have accepted digital evidence as “business records” under the business records exception rule, assuming that the evidence was gathered correctly and is accurate. [16]

Case laws

One of the sources of laws is case decisions or precedence. It’s important for us to look at digital forensics cases and how they have changed the field.

U.S. v. Bonallo

One of the main issues with digital evidence is authenticity. Although the evidence collected can be considered authentic and verified because of the hashing, someone could always say that original data was tamped with or implanted. An argument can be made that because the computer evidence is susceptible to tampering or implantation of evidence, it should not be admissible.

Daniel Bonallo was an employee at American Data Services. He worked on Automated Teller Machines and Bank Card Management Systems. American Data Services handled data processing for The Oregon Bank. In 1985, the bank started receiving complaints of unknown withdrawals. The bank realized that someone had made 40 fraudulent transactions.  Bonallo was the main suspect because he was an expert on ATM and bank systems. Most of the fraudulent transactions happened on ATM’s located between Bonallo’s house and American Data building. Bonallo also completed transactions at an ATM outside of American Data building.

The person who was handling Bonallo tasks testified and said that he found a “fraud program” on Bonallo’s computer. This program allowed a person to access ATM’s file system and change transaction records. Although, he also said that the program had legitimate uses. Bonallo denied making transactions and existence of “fraud program.” He claimed that he was framed.

Bonallo made the argument discussed previously. He claimed that evidence was not trustworthy because someone had altered it to frame him. Bonallo failed to provide evidence that supported his alteration claim. The evidence was in fact admissible because “The fact that it is possible to alter data contained in a computer is plainly insufficient to establish untrustworthiness. The mere possibility that the logs may have been altered goes only to the weight of the evidence not its admissibility.”

U.S. v. Glasser

U.S. v. Glasser is a similar case to Bonallo v. U.S. In this case, the focus is on security of a system and how it relates to alteration of a system. In this case, Jodi Glasser is charged with embezzlement and making false entries in bank records. Trustworthiness of the records was questioned in this case. The evidence or the computer printouts were admissible because “The existence of an air-tight security system is not, however, a prerequisite to the admissibility of computer printouts. If such a prerequisite did exist, it would become virtually impossible to admit computer generated records; the party opposing admission would have to show only that a better security system was feasible.” [17]

U.S. v. Crist

In 2005, a landlord hired two people, Jeremy Sell and Kirk Sell, to remove tenant’s possessions. The tenant, Robert Crist, was unable to pay the landlord so landlord requested the removal of his belongings. Jeremy and Kirk Sell started putting most of Crist’s belongings on the curb. In August, Jeremy Sell gave a computer that belonged to Crist to his friend Seth Hipple. When Crist came back home, he asked where his computer was. The Sells decided not to tell Crist about his computer being given to Hipple. Crist called the police and reported that his computer was stolen.

Hipple, after getting the laptop, searched for things he could delete. While cleaning the computer, Hipple came across child pornography, deleted the folder containing it, and turned the computer off. Few days after this incident, Hipple contacted the police department and reported what he did. Detected Michael Cotton was assigned to handle this investigation. The detective was told who the computer belonged to and he also knew that it was reported stolen. The detective contacted Attorney General’s office to have the computer forensically analyzed. Attorney General’s office took the computer and gave it to David Bushwash, an agent in computer forensics department, to examine.

Bushwash followed the standard forensic examination procedures and created a clone image of the harddrive. Bushwash started analyzing the clone image with EnCase. EnCase performed MD5 hash algorithm on all the files that the clone image contained and matched with known hash list. Some of the files matched with known child pornography list. After the analysis, Bushwash reported to detective Cotton. Crist was charged with possession of child pornography.  Crist filed motion to suppress the evidence. One of the main issues in this case was that the forensic examiner ran MD5 hashing algorithms on the files. The act of running hashing algorithm was a search. The court ordered to suppress all the evidence obtained from the forensic examination. [18]

In re Boucher

Software manufactures have been making software that allows a person to easily encrypt their data. For example, Microsoft started including full-disk encryption feature, BitLocker, in some versions of their operating systems starting in 2007. Free and reliable encryption software was available before 2007, but they were generally hard to setup, or use. Many encryption tools did not allow you to encrypt the whole harddrive; instead they allowed you to encrypt folders or specific files. Microsoft’s BitLocker allowed users to setup full-disk encryption in just a few clicks. This is different from password protection, since password protection is only in play when the computer is running. When a computer is password protected, it can be turned off and an examiner could still access all the files. An examiner now had the challenge of dealing with fully or partially encrypted data.

Sebastien Boucher was traveling from Canada to United States. At the border station his car was inspected. This is allowed because of the Border Search Exception mentioned previously. Officer doing the inspection saw that there was laptop in the car. When the officer opened the laptop, it was not password-protected. Officer started to search the computer for images and videos and found around 40,000 images, and some of them had pornographic file names. Officer asked Boucher if his laptop contained any child pornography. Boucher replied that he was not sure. Officer noticed that file names looked like they could contain child pornography. Officer called Immigration and Customs Enforcement officer, who had training in identifying child pornography. ICE agent started to examine the laptop. He determined that the computer did contain child pornography. Agent read Miranda Rights to Boucher, and Boucher waived them. Agent asked Boucher about the file “2yo getting raped during diaper change” and Boucher replied that he downloads many pornographic files, but when he sees a file containing child pornography, he deletes it. At the agents’ request, Boucher showed him where the files were stored. Files were stored in drive Z, and it didn’t require password to access them.

After doing more examination, agent calls US Attorney’s office and then seizes the laptop. In this process, the agent also shut the laptop down. When the laptop was provided to an examiner, they noticed that they were unable to access the Z drive because it was encrypted. Grady jury sent a subpoena to Boucher telling him to provide passwords. Boucher quashed the subpoena because it was violating his 5th amendment rights. Magistrate judge handling the case agreed that providing the passphrase/password to the encryption harddrive would be self-incrimination. Passphrase would be considered product of the mind and testimonial communication, therefore he does not have to give it up. This issue is often compared with a combination lock vs. traditional lock with a key.[19] Key already exists, but the combination to a lock can be in your mind or can be in your mind.

In 2009, a different court ruled that Boucher does have to give up the passphrase. It was ruled that the act of production (of the passphrase) cannot be used to prove that Boucher owned the laptop or data. Court would now need to use an alternative way to prove that Boucher owned the laptop. [20]

Another rule that can apply to encryption cases is foregone conclusion exception. Under foregone conclusion exception, the 5th amendment no longer applies because the evidence is not considered testimonial. If the government already knows that files exist, and exactly where they exist, foregone conclusion is valid. [21]

Famous cases with digital evidence

BTK Killer

BTK Killer or Dennis Rader killed ten people in Kansas. Rader sent letters to the police asking if a floppy disk could be traced or not. The police published the answer in the newspaper saying that “Rex, it will be OK”, which told Rader that it was safe to do so. Rader sent a floppy disk to KSAS-TV. The floppy disk contained a file with message “this is a test.” The examiners recovered deleted files from the floppy disk and looked at metadata to discover that author was Dennis. Other recovered data indicated that the computer used to write the file was owned by Christ Lutheran Church. After internet search, the police determined that Rader was part of the church. The police also had evidence that the killer had black Jeep Cherokee. Investigator noticed that Rader had the same car. In this case, digital evidence examination helped the police track down the killer.  [22]

Caylee Anthony Case

This case is perfect example of some of the problems that can occur with digital evidence examination. John Bradley was one of the witnesses who conducted digital evidence examination. Prosecution said that the word “chloroform” was searched for 84 times. Bradley later discovered that the software didn’t correctly handle the forensic data, and the search was only made once. During cross-examination Bradley also agreed with the defense saying that there were two different accounts on the computer and there was no way to tell who searched for “chloroform.” Forensic software can cause issues sometimes, but this can be avoided by validating the tool and by using Daubert Standards. The tool has to be tested by other people, has to be peer-reviewed, has to be checked for error rates or potential problems, and be generally accepted by the community. [23] A lab could use a dataset and use the examination tool to see if the output matches the expected results. Even if the tool valid and accepted, it would be good to have internal testing. [24]

After the trial was over, the police reported that they never looked at history of Firefox browser; they just looked at Internet Explorer history. When the police did search Firefox history, they saw that someone searched for “foolproof suffocation” and clicked on article about committing suicide. [25]

Problems and challenges

One of the main problems is encryption. Encrypting data has become easier over the past few years; it can accomplished by clicking a few buttons. Examiners now have either limited amount of data or have to go through the legal system to get the unencrypted data. This is not to say that encryption is a bad thing or only the criminals do it.

Cloud computing or cloud storage is another issue. Cloud refers to things being done on remote servers. If someone is using cloud storage to store their data, they are storing the data on some remote server, such as Dropbox or Box. There are service providers who monitor user in order to see if anything illegal has been transmitted. Apple has iCloud service with keyword and phrase detection. When a keyword or phrase is detected in an email, it automatically deletes it. [26]

Anti-forensics and covert channels are also a problem. Although these both things have legitimate uses, they have been used to do illegal things. Tor or The Onion Router allows a user to browse the web anonymously. Tor also allows a person to setup an anonymous server. Silk Road was an online website, similar to Amazon or eBay, which was used to sell illegal services or things. It was mainly used to sell drugs.[27] There are also sites similar to Silk Road, which are used to sell weapons. Last year, the FBI was able to take down Silk Road and arrest the administrator of the website. [28] This is probably the only field that has anti-forensics side. Digital forensics can be used by a criminal to recover confidential data or gather intelligence for an attack. Anti-forensics techniques are developed to deal with this issue, and these methods can also be used by criminals. As discussed before, encryption is a good method to stop digital forensics. A criminal could also securely delete their files. There are ways to hide data using methods such as steganography. Criminal could also directly attack the forensic software. This is only a big issue when the criminals are very sophisticated.[29]

Conclusion

In this paper, I discussed: how digital forensics works, laws and case laws that apply to digital evidence, famous cases that had digital evidence, and problems with digital evidence.

From what I’ve researched for this paper, I believe that the courts are doing a good job dealing with digital evidence. Digital evidence is not too different from other evidence. Most of the times 4th amendment and Federal Rules of Evidence apply to digital evidence. Case laws only apply in rare cases. With rise in use of internet, cloud storage, and encryption, it will be interesting to see what other changes come to this field.

Resources

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"General Information: Florida Computer Crimes Act." from http://docweb.cns.ufl.edu/docs/d0010/d0010.html.

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(2012). "Casey Anthony detectives overlooked Google search for "fool-proof" suffocation methods, sheriff says." from http://www.cbsnews.com/news/casey-anthony-detectives-overlooked-google-search-for-fool-proof-suffocation-methods-sheriff-says/.

(2013). "Piecing Together Digital Evidence The Computer Analysis Response Team." from http://www.fbi.gov/news/stories/2013/january/piecing-together-digital-evidence/piecing-together-digital-evidence.

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Cases

·        U.S. v. Bonallo

·        U.S. v. Crist

·        U.S. v. Glasser

·        In re Boucher

·        BTK Killer

·        Caylee Anthony Case

Rules/Law

·        4th amendment

·        5th amendment

·        Border Search exception

·        Business record exception

·        Computer Fraud and Abuse Act

·        Federal Rules of Evidence rules 803, 1002, 1003

·        Florida Computer Crimes Act

[1] http://www.internetworldstats.com/stats.htm

[2] http://www.internetlivestats.com/internet-users/

[3] http://www.theconnectivist.com/2014/05/infographic-the-growth-of-the-internet-of-things/

[4] http://www.mekabay.com/overviews/history.pdf

[5] http://www.historyofinformation.com/expanded.php?id=3888

[6] http://docweb.cns.ufl.edu/docs/d0010/d0010.html

[7] https://ilt.eff.org/index.php/Computer_Fraud_and_Abuse_Act_(CFAA)

[8] http://www.fbi.gov/news/stories/2013/january/piecing-together-digital-evidence/piecing-together-digital-evidence

[9] https://www.swgde.org/pdf/2003-01-22%20SWGDE%20History.pdf

[10] http://www.nij.gov/publications/ecrime-guide-219941/ch5-evidence-collection/Pages/welcome.aspx

[11] http://codeidol.com/community/security/md5sum-and-md5-validating-the-evidence-collected/22551/

[12] http://www.forensickb.com/2014/02/enscript-to-create-encase-v7-hash-set.html

[13] http://www.computerworld.com/article/2487636/data-privacy/justices-let-stand-appeals-court-decision-on-border-searches-of-laptops.html

[14] http://www.nytimes.com/2013/09/10/business/the-border-is-a-back-door-for-us-device-searches.html?pagewanted=all&_r=0

[15] http://euro.ecom.cmu.edu/program/law/08-732/Evidence/RyanShpantzer.pdf

[16] http://www.infosecwriters.com/text_resources/pdf/Computer_Forensics_to_Court.pdf

[17] http://leagle.com/decision/19852326773F2d1553_12113.xml/UNITED%20STATES%20v.%20GLASSER

[18] http://www.volokh.com/files/USA_v._Crist,_order-1.pdf

[19] http://blogs.denverpost.com/crime/2012/01/05/why-criminals-should-always-use-combination-safes/3343/

[20] http://volokh.com/files/BoucherDCT.1.pdf

[21] http://www.slate.com/articles/technology/future_tense/2012/03/encrypted_files_child_pornography_and_the_fifth_amendment_.html

[22] http://www.theatlantic.com/technology/archive/2014/01/the-floppy-did-me-in/283132/

[23] https://www.cerias.purdue.edu/bookshelf/archive/2005-17.pdf

[24] http://www.dfinews.com/articles/2011/03/validation-forensic-tools-and-software-quick-guide-digital-forensic-examiner

[25] http://www.cbsnews.com/news/casey-anthony-detectives-overlooked-google-search-for-fool-proof-suffocation-methods-sheriff-says/

[26] http://www.huffingtonpost.com/cassie-slane/yes-your-cloud-storage-pr_b_2853948.html

[27] http://www.telegraph.co.uk/technology/internet/10635359/Drugs-guns-and-assassination-Silk-Road-successor-Utopia-shut-down-by-police.html

[28] http://www.usatoday.com/story/news/nation/2013/10/21/fbi-cracks-silk-road/2984921/