The Malware and Unattributed-Download Defense: When It Works.

Last Updated on: 4th August 2026, 01:33 am

At Spodek Law Group, we can use the unattributed files defense (as well as the malware defense) whenever it makes sense to do so in order to challenge the government’s evidence of knowledge, access, or control.

The unattributed files defense is most relevant when knowledge or control is at issue. That said, the fact that unattributed files are technically possible does not alone establish unauthorized downloading or control, just as the fact that a defendant owned a computer on which the files were found does not establish unauthorized downloading or control.

Prosecutors are burdened with proving every element of a crime beyond a reasonable doubt. When forensic evidence clearly shows that the defendant knowingly downloaded, accessed, or controlled the files, courts often reject unsupported hacker theories.

Some federal online sex offenses also require proof that the defendant knew (or was recklessly indifferent to) the true age of the victim, or that the victim appeared to be at least 18. Evidence that the victim consented to access the computer system in question can also defeat unauthorized-access allegations under the Computer Fraud and Abuse Act and similar statutes.

Entrapment defenses also become available in some online cases when law enforcement agents induce defendants to commit online crimes they were otherwise unlikely to commit.

Insufficient evidence can instead support a judgment of acquittal to some (but not all) statutory online offenses, which typically target defendants’ state of mind. When a defendant has no actual knowledge that illicit files were downloaded to their device, or any reason to believe that their device was being used to communicate or interact with another individual for illegal purposes, federal prosecutors can fail to meet the necessary standard of proof.

Is Malware Itself a Crime in Federal Court?

The FBI is the leading federal investigative agency for computer-crime statutes. Federal cybercrime prosecutions are generally brought by the United States Attorney’s Office in the district in which the crime is alleged to have taken place, and federal criminal charges are prosecuted in federal district court (as opposed to state criminal charges, which are prosecuted in state courts). Federal jurisdiction is established when there is (among other grounds) interstate activity, and this includes the use of a “federal computer system” in violation of federal law.

While “malware” is not a crime in and of itself, the use of malware can be criminal depending on the purpose or intent involved. If the malware is used to establish unauthorized access to a protected computer, cause damage to the computer, defraud the computer’s owner, or extort the computer’s owner, then the use of the malware could be criminal. For example, accessing another person’s computer or network without permission is a crime under both state and federal law.

The Computer Fraud and Abuse Act (or “CFAA”), enacted in 1986 as an amendment to the Counterfeit Access Device and Computer Fraud and Abuse Act of 1984, is the principal federal statute targeting “unauthorized access” to computers; the term “protected computer” was introduced by the 1996 amendments. The CFAA has been amended several times since its original enactment, and many states have enacted similar statutes in response to evolving threats. With these statutes and federal law, accessing another person’s computer without permission is a criminal offense. It is also a criminal offense to engage in “unauthorized access” to a computer with intent to defraud, cause damage to, or obtain information from that computer, among other specific targets of the CFAA.

What Proof Makes the Malware Defense More Than Speculation?

To move a malware or unattributed files defense beyond mere speculation, you need evidence that links the computer’s suspected compromise specifically to the charged conduct. You cannot just say, “The FBI says there is malware on my computer and I was charged with a crime, so the malware must have caused the crime.” Instead, you need evidence showing that the malware (or other form of compromise) had the capability, the privileges, the timing, and the network access required to cause the conduct at issue.

For example, if you were infected with malware after the alleged download of illicit content occurred, then the malware infection did not cause the download. However, you can use artifacts such as infection timestamps and persistence artifacts to show that a malware infection happened prior to the alleged crime. This evidence may be necessary to avoid appearing as if your computer were “used” to communicate with a person for an illegal purpose.

What Do Digital-Forensics Experts Do?

A forensic expert who is familiar with the capabilities and limitations of the malware in question, as well as with the capabilities and limitations of the computer system in question, can explain why certain downloads were unintended or why the defendant did not have control over the computer system.

Federal Rule of Evidence 702 governs the qualifications, duties, and limitations of a digital-forensics expert. When testifying in state court in a “Frye jurisdiction,” the expert’s methodology must also be “generally accepted.” The expert’s methodology will include the examination of forensic artifacts that leave a footprint when software (and hardware) is run. The expert can then explain the footprint left by malware that was used to download illicit files, establish unauthorized remote control, or perform the computer system’s automatic-updating, which may have resulted in an unintended download.

As digital forensics continues to evolve, so too does the skill set required to provide a comprehensive forensic analysis for online criminal cases. With that, the role of a digital-forensics expert in a federal criminal case is critical when faced with criminal accusations involving unauthorized or unintended downloads and control.

When Does Digital-Forensics Evidence Matter Most in Online Criminal Cases?

Digital-forensics evidence that establishes a “plausible” alternate scenario for the defendant’s alleged criminal conduct is valuable in all online cases. In some cases, forensic evidence can establish more than a “plausible” alternate scenario. If the evidence is legally insufficient, a trial judge may enter a judgment of acquittal.

In other cases, however, showing plausible uncertainty can be enough to give prosecutors reason to rethink their charges or the federal case’s worth. In many cyber-defense cases, forensic experts present plausible uncertainty in hopes of influencing federal charging and plea negotiations.

Which Forensic Artifacts Can Distinguish Between Intentional and Unintentional Downloads and Control?

The examples of forensic artifacts listed above are only some of the clues digital-forensics experts use to piece together a defendant’s alleged online conduct in cyber-defense cases. For each of these artifacts, digital-forensics experts can examine how their creation would correspond to the activities alleged in the criminal complaint.

How Will a Digital-Forensics Expert Prove Intent?

A digital-forensics expert can prove (or disprove) a defendant’s intent by examining forensic evidence and artifacts such as:

• Browser History and Download Manager Records, Browser history and download-manager records are key sources of evidence that can distinguish directed downloads from automatic ones.
• Windows Prefetch Files, Windows prefetch files can help establish what programs were run and when, which in turn helps establish whether relevant programs executed prior to any alleged download.
• Windows Shortcut Files, Windows shortcut files (.lnk) record the time and date a file was accessed, the path where it is located, the device it is on, and how the user accessed it. This makes shortcut files incredibly useful for proving or disproving intentional or unintentional downloads.
• Shellbag Artifacts, Shellbags can provide evidence that a user navigated to and opened specific folders.
• Antivirus and Quarantine Records, The presence of malware can be proven by checking the system’s antivirus and quarantine records. If the antivirus or quarantine records show that a security tool detected or removed malware before the system was seized, this information will be extremely useful for the defense.
• Peer-to-Peer Configuration Files, Many websites and online communication systems rely on peer-to-peer networking or peer-to-peer file sharing. Many peer-to-peer configuration files include the information about automatic downloading, which may provide evidence of unintended acquisition.

How Will a Digital-Forensics Expert Prove Content?

Digital-forensics experts rely on digital-forensics artifacts to prove content (and the illegal nature of that content), regardless of whether the evidence establishes an intentional or unintentional act of downloading. Here are some examples of digital-forensics artifacts that can prove content:

• File Hash, A file hash allows investigators to confirm that a file is indeed what they think it is, and that the content of the file is not something that is unknown or unidentified. A file hash cannot, however, identify who placed the content on the computer.
• File Metadata, The metadata found in most files can show file creation, modification, and acquisition, and sometimes even the device where the file originated.
• File Header, As noted above, file headers can be used to determine whether an illegal file is stored in its native file format or has been renamed (obfuscated). A file header can also indicate the source device or source application that produced the file.

This is the point at which most people call a lawyer. Spodek Law Group takes federal criminal defense cases nationwide from its New York and Los Angeles offices.

How Can Prosecutors Establish “Knowing” Control Despite Claims of Malware Downloads, a Drive-By Download, or Malware-Induced Control?

1. “The Defendant Knew He/She Received the Content, and He/She Didn’t Delete It After Receiving It”

In cases involving allegations of computer use for child pornography, federal prosecutors’ theories of knowing control generally start from the fact that the defendant received the illicit files (by any means), and the fact that he/she failed to delete the files. Prosecutors then argue that the defendant either knew the content of the files at the time of receipt (or developed knowledge after receipt) and thus continued to knowingly retain control of them. The “unattributed files” defense is a complete defense only if the forensic evidence not only provides an explanation for the receipt of the files, but also rebuts the theory of knowing retention.

2. “The Defendant Kept the Files, Opened and Reviewed Them, Organically Organized the Files, Renamed the Files, and Searched the Files”

In some cases, the forensic evidence will include artifacts showing repeated searches, access to the content, organization, and renaming of files. These activities can be used by the prosecution to support an inference of the defendant’s knowledge.

3. “The Defendant Attempted to Delete the Files”

The evidence that a defendant attempted to delete (but failed to successfully delete) a known-child pornography image or other illegal file from their device can also be used by the prosecution to support an inference of the defendant’s knowledge of and control over the file.

4. “The Defendant Viewed the Files or Retained Them on the Device in an Easily Accessible Format”

While thumbnail databases like the thumbnails.db file may corroborate that a defendant’s computer system displayed the image files contained in the system’s thumbnail folder, they cannot identify the user that displayed them.

5. “The Defendant Logged in With a Password, Accessed the Computer, and Set Up the Drive to Share Files”

If prosecutors can show that the defendant logged into the computer with a password and set up a peer-to-peer networking connection through which the files were downloaded (and later shared with others), this is strong evidence of the defendant’s dominion or intentional sharing.

The drive-by cache theory deals only with the automatic storage of a computer system’s cache of a page when a browser is used to open a website that automatically downloads the images within the cache, and that cache is not clear. This does not mean that the images were automatically uploaded to a folder, nor does it mean that the images could not have been accessed by the defendant. Even if the drive-by cache theory explains why an image was downloaded, it does not rebut the evidence of the defendant’s knowing retention of the image.

6. “The Defendant Possesses Deleted Files That Are Reconstructible With Forensic Software”

The evidence of recovery of a deleted file via digital-forensics software can establish an illegal file, it cannot alone establish that the files were not deleted by the defendant. As with other forms of control, the fact that a file has been recovered only establishes that the content of the file was previously stored on the device, not that the defendant knowingly retained control of it or knowingly accessed it.

What If Another User, Account, or Another Network Caused the Illegal Downloads or Control?

1. Another Individual Had Physical Access to the Device or Account

For cases involving shared computers or mobile devices, establishing a chain of custody is not enough to establish that the defendant had control over a specific action. In other cases, if someone else has physical access to the computer or account (with or without a password), this may create a defense to a particular act. The evidence showing the use of a shared family computer or account logged in when an unauthorized act was committed can make the prosecution’s case tenuous.

2. Another Individual Had Unauthorized Remote Access to the Device

When another individual has unauthorized remote access to a computer system, they can download, move, modify, and delete files, as well as use the computer system for online communications. This can be accomplished via a computer Trojan horse, other forms of malware, or simply through a password breach or session hijacking. If the forensic evidence showing the presence of unauthorized remote control coincides in time and capability with the charged offense, then a compelling defense is available to the defendant.

3. Someone Stole the Defendant’s Online Account (but not necessarily the device)

If another individual stole the defendant’s online account, they can use that account to communicate with others, download a file (even if they store that file on their own computer), and perform any other activity enabled by the online account. The evidence showing the use of another individual’s online account does not establish that the files were stored locally on a device belonging to the defendant. As with the drive-by cache theory, this evidence cannot be relied upon for establishment of a guilty finding in online child pornography cases.

4. Someone Used a Compromised Network

An open Wi-Fi network, a compromised Internet Service Provider (ISP), or an open network that had been hacked can provide a plausible explanation for IP attribution. However, using the defendant’s IP address can just provide circumstantial evidence that a particular person used a computer that was connected to that network. To rebut a criminal charge, the defendant needs to use digital-forensics artifacts such as remote-access logs, persistence artifacts, or evidence from other devices to corroborate that the downloads were made by someone else.

5. Other Family Members, Employees, or Colleagues Had Shared Use of Accounts

When multiple people (including other members of the same household) share an account, shared content can be synchronized across their devices. Even if this was not the intent, it could happen, and this could mean that some files may appear to have been acquired or retained by the defendant. This may also be the case when a defendant and other individuals (such as a family member or an employer) handed off a device to another person to use for a time. Again, establishing the timing of handoffs is essential to showing that the defendant did not have control over any illegal file acquisition, use, or retention.

What Should Defense Counsel Preserve (and Ask Law Enforcement to Preserve) Before Logs and Other Evidence Disappear?

Proving (or disproving) unauthorized or unintentional downloads or control depends on the timing, duration, and nature of the defendant’s possession and use of computer systems. To achieve these goals, defense counsel should work with a digital-forensics expert to ensure that a forensic image of the device(s) has been preserved. Unlike traditional “backups,” a forensic image of a computer, mobile device, or other device preserves the state of the computer and allows for repeatable examinations by the government and the defendant’s experts.

For cases in which a device is seized before it is powered down, the device must be isolated from any network (via a faraday cage or network isolation), or a remote user may attempt to wipe a device, change data, or use a legitimate remote access password to disable the access to relevant data. Digital-forensics evidence that has not yet been collected cannot be recovered once it has been overwritten (by the device owner or by others) or deleted by an operating system as a result of automatic deletion, as is common with log files on Windows and other operating systems.

Computer logs provide a detailed history of when specific artifacts were created, stored, and deleted, and what programs were opened, downloaded, or shared. This is evidence that is invaluable for proving unauthorized activity. When a device is seized, then powered down, it cannot be touched or modified, but its contents can be imaged. Continued use of a seized computer can overwrite data, rotate logs, and change user-created dates and times, all of which can compromise a defendant’s ability to prove or disprove the charges at hand.

Digital-forensics experts must also preserve evidence of potential antivirus cleanups, operating system updates, and other interventions. Digital forensics is essentially a contest of who has a clear (and corroborated) picture of the illegal files and when they were made available. A factory reset of a mobile phone or other devices can also wipe the devices of critical (and potentially exonerating) evidence.

When forensic technicians create forensic images, any changes must be documented. This includes access timestamps. Also, whenever possible, they should capture router logs. While these logs can be used to identify the device connected to a particular network, the information they reveal about IP addresses and connected devices can quickly disappear.

Can Any Additional Efforts and Evidence be Used to Defeat Charges of Possession?

There are some additional efforts and other forms of evidence that can work to support a defense to a charge of illegal content possession. Digital evidence is complex, and forensic software is not perfect. Many successful digital-forensics challenges involve an expert debunking an opponent’s analysis of the data, pointing out a failure in the forensic process, or showing that the data was collected in an manner that violates constitutional standards. This includes arguments that the digital evidence was collected pursuant to a flawed search warrant, and this can support suppression of the evidence obtained via the flawed warrant.

Talk to Spodek Law Group

Every case turns on its own facts, and general information is no substitute for advice about yours. Todd Spodek, managing partner of Spodek Law Group, and the firm's attorneys defend federal criminal and white collar matters nationwide. Reach the firm at 212-300-5196.