Malicious Email Attachments

Malicious email attachments are files sent with emails designed to compromise or damage the recipient’s computer system or exfiltrate sensitive information. These harmful payloads can masquerade as innocuous items—documents, PDFs, images, or audio files—that, when opened, unleash malware, such as ransomware (which locks access to data until a ransom is paid), spyware (that stealthily collects and transmits personal information without consent), or viruses (designed to corrupt systems and spread to other devices).

The deceitful nature of malicious email attachments lies in their presentation. They’re often cleverly disguised as legitimate communications from reputable sources, which increases the likelihood of unsuspecting users opening them. Attackers frequently employ file types like .exe (executable files), .zip, .rar (compressed folders that may contain malicious content hidden within multiple layers), or .7z for their nefarious purposes. These formats offer versatility in concealing malicious code and facilitating its execution upon user interaction. Awareness of these common vectors is crucial for individuals to safely navigate their digital environments.

Malicious email attachments are designed to launch an attack on a user’s computer. They deceive users into opening files that appear harmless but contain malware. Here is how they typically operate:

• Disguised content: Malicious attachments are disguised as important documents, invoices, advertisements, or other seemingly legitimate files to entice users to download and open them.
• Exploiting software flaws: Attackers hide software called “exploits” within commonly sent files like Microsoft Word documents, ZIP or RAR files, PDFs, images, or videos. These exploits take advantage of software vulnerabilities to download malicious software (payload) onto the victim’s computer.
• Social engineering: Attackers use social engineering tactics to persuade users to click on malicious macros or enable content in the attachment, ultimately infecting the victim’s computer with malware like ransomware.
• Payload delivery: The payload delivered through the exploit can allow attackers to control the user’s computer, capture keystrokes, access network systems, steal information, or cause damage by overwriting files and deleting data.
• Enable Content: Attackers can also embed a malicious macro in the document and use social engineering to trick the user into clicking the “Enable Content” button that allows the macro to run and infect the victim’s computer.

Attackers typically send these email attachments with sufficiently convincing content so the user believes it is legitimate.

Opening a malicious email attachment can unleash a Pandora’s box of digital threats, each with its own set of repercussions for the individual or organisation. The risks are not just confined to the immediate device but can ripple through entire networks, leading to widespread compromise and disruption.

Infection with Malware

One of the primary threats associated with malicious attachments is the deployment of malware upon their execution. Malware encompasses various forms of harmful software, including:

• Viruses: These self-replicating programmes infiltrate systems to corrupt files, hinder performance, and spread across connected devices.
• Ransomware: By encrypting data on infected machines, ransomware holds information hostage until a ransom payment—often in cryptocurrency—is made.
• Spyware: Operating covertly, spyware gathers sensitive data (passwords, financial information) without consent for unauthorised purposes.

System Compromise

Beyond initial infection lies deeper system compromise. Malicious attachments can be gateways for attackers to gain unauthorised access to systems and networks. Once inside, they may establish advanced persistent threats or “backdoors” that allow continued access even after initial breaches are discovered and ostensibly remedied. Critical system functionalities could be disabled or manipulated, impacting business operations or personal use.

Data Breach and Theft

A particularly insidious risk involves data exfiltration—or theft—of confidential information:

• Personal identity details such as social security numbers or banking information could fall into criminal hands.
• Corporate espionage might occur if proprietary business strategies or intellectual property are stolen.

Propagation Across Networks

Devices rarely operate in isolation. In turn, an infected machine poses a threat not only to itself but also acts as a vector, spreading malware throughout local networks—and potentially beyond—to clients’, suppliers’, or partners’ systems.

What seems like an innocuous click on an email attachment can serve as a linchpin for myriad cybersecurity concerns spanning from individual privacy invasions to comprehensive organisational disruptions.

Identifying malicious email attachments before inadvertently triggering their harmful payloads is a critical skill in the digital age. The average user can enhance their defences by honing their eye for telltale signs that suggest an attachment may not be as benign as it appears, such as:

• Unexpected senders or content: If you receive an email with an attachment from someone you don’t recognise or weren’t expecting communication from—especially if it prompts urgent action—scrutinise it further.
• Inconsistencies in email addresses: A common tactic among attackers is to spoof familiar addresses with slight alterations. Carefully inspect the sender’s address for subtle misspellings or unusual characters that might betray its illegitimate nature.
• Generic greetings and typos: Professional organisations typically personalise emails using your name rather than generic salutations like “Dear Customer”. Additionally, many spelling or grammatical errors can indicate phishing attempts.
• Suspicious file extensions: As mentioned previously, unexpected executable files (.exe), compressed folders (.zip, .rar), and even document formats (.docm indicating macros) should raise red flags. Be particularly wary of double extensions (e.g., “report.pdf.exe”) designed to deceive users into thinking a file is safe.
• Unsolicited requests for sensitive information: Legitimate entities will not ask you to provide sensitive personal information via email attachments. Consider any such request highly suspect.
• Use of fear tactics: Be cautious about emails leveraging fear by threatening account closures or legal actions unless immediate steps are taken—including opening an attachment.

Honing these observational strategies involves cultivating a sceptical mindset when dealing with incoming emails with attachments.

When it comes to ensuring the safety of an attachment before downloading or opening it, adopting a vigilant and methodical approach is key. Here are comprehensive steps to help you avoid opening a malicious email attachment:

• Examine the sender: Start by scrutinising the sender’s email address for any signs of suspicious activity. Genuine emails typically have consistent domain names relevant to the organisation they claim to represent. If you notice odd characters, misspellings, or unfamiliar domains, proceed with caution.
• Assess email content: Look beyond who sent the email; pay attention to its overall tone and language. Phishing attempts often contain urgent requests for personal information or actions like clicking on links or downloading attachments under pretences that seem alarming.
• Hover before you click: Position your cursor over any link in the email (without clicking) to preview where it leads. A legitimate link will usually display a URL matching known websites associated with the sender’s purported identity—any deviation should raise red flags.
• Use antivirus software: Ensure that your antivirus software is up-to-date and has real-time scanning capabilities enabled. That provides another layer of defence if you decide an attachment seems safe enough to download.
• Check file extensions carefully: Certain file types pose more risk than others primarily because they can execute code that could be malicious. Examples include .exe, .scr, and .zip files, among others. Always question why someone would send such files unless explicitly expected as part of ongoing communications.
• Employ attachment scanning tools: Several online tools are designed explicitly for analysing potentially harmful attachments without opening them on your device first. These platforms work by uploading said document into their environment to conduct various checks against known malware signatures.
• Seek expert advice when unsure: If you’re still uncertain about an attachment’s safety after applying all known checks and precautions, don’t hesitate to consult with IT professionals or cybersecurity experts. This step is particularly crucial in a business environment where the implications of opening a malicious file can be far-reaching.
• Stay informed about cybersecurity trends: Knowledge is power, especially when it comes to cybersecurity. Regularly educating yourself on the latest threats and scams circulating online equips you with the required foresight to spot potential dangers before they impact you or your organisation.
• Only download attachments over secure networks: Always ensure that you are connected to a secure network before downloading any attachments—preferably one that is encrypted and password-protected (like your home or work Wi-Fi). Public networks at places like cafes or airports often lack sufficient security, making them hotspots for cybercriminals looking to intercept data.

Integrating these strategies into your routine when dealing with incoming attachments can significantly reduce the chances of falling victim to cyber-attacks.

To protect against malicious email attachments, start with user education but back it up with email attachment security solutions.

• Set up a secure environment: Establish a secure environment for your data and network, as malicious attachments can include self-replicating worms, trojans, ransomware, and other malware. Your email infrastructure plays a crucial role in maintaining security. Proofpoint’s Email Security and Protection solution is a world-class product that handles much of the heavy lifting to keep your organisation and people protected.
• Scan incoming emails: Regularly scan incoming emails for malicious attachments by verifying the source of the email, running antivirus scans, and using preview options offered by most email service providers.
• Using a spam filter: Spam filters scan emails for certain criteria and assign them a score based on their likelihood of being spam or containing malicious content. These filters can help prevent malicious email attachments by filtering out potentially harmful content before it reaches the recipient’s inbox.
• Practice good password hygiene: Prevent attacks like password collectors and keyloggers by changing passwords frequently and creating strong passwords with a combination of sentences, different cases, special characters, and numbers. Consider investing in a credible password manager.
• Avoid opening emails from untrusted sources: Refrain from opening emails from untrusted sources, as cybercriminals often use social engineering tactics to trick users into clicking on malicious attachments.
• Turn off automatic downloads: Disable automatic downloads for email attachments to prevent malware from automatically executing upon opening an attachment.
• Stay alert and aware: Remain vigilant and combine security protocols with employee education to recognise and report any suspicious email attachments that may contain malware.

By implementing these practices, individuals and organisations can enhance their defences against malicious email attachments and reduce the risk of falling victim to cyber threats.

For optimal results, look for a security solution that scans email attachments in the cloud via static and dynamic (sandbox) malware analysis before they’re delivered. That way, email attachments are checked for bad behaviour, not just known bad reputation or known signatures, which tend to miss zero-day and polymorphic malware attacks.

Opening a malicious email attachment can inadvertently set off a chain of undesirable events on your computer or network. These nefarious programmes can compromise personal data, lock you out of your files, and even use your system as part of larger network attacks without your knowledge.

Firstly, if you suspect that the attachment opened is malicious—immediately after opening it or upon noticing unusual computer behaviour—disconnect from the internet. This is critical because it prevents the potential malware from transmitting sensitive information back to its creator or downloading additional harmful components onto your device.

Next, initiate a full system scan using reputable antivirus software. Ensure that your security software is up to date before this action—the latest definitions are paramount in effectively detecting and removing recent threats.

Should the antivirus find and quarantine threats, follow its recommendations for removal but remain vigilant. Some sophisticated malware might evade initial detection or have already inflicted damage requiring professional attention.

After dealing with immediate threats:

• Change all passwords using another device deemed safe—a precaution against possible data theft. Consider using a password generator to ensure you use strong and secure passwords.
• Monitor financial accounts for unusual activity if sensitive information could have been compromised.
• Consider contacting an IT professional specialising in cybersecurity for an in-depth analysis and recovery efforts if necessary.

Lastly, educate yourself on cybersecurity best practices. Understanding the evolving threat landscape empowers you to navigate digital communications responsibly.

These cases highlight the diverse methods cybercriminals use to exploit email attachments for financial gain or data theft, emphasising the importance of robust cybersecurity measures to combat such threats.

These products from Proofpoint help organisations defend against evolving threats like BEC scams, phishing attacks, and advanced malware delivered through email attachments. To learn more, contact Proofpoint.