Businesses rely on emails to run teams smoothly, communicate with customers, and keep managers in the loop. But what if emails go rogue? Could the next email you open infect your network with ransomware or spyware agents?

Sadly, the answer is yes. A single email can compromise an entire business network. Clicking attachments or following fake links can lead to identity theft attacks, malware infestations, data loss, and, eventually, financial damage.

Email security is a critical concern for every business. Let’s cut through the myths surrounding email phishing attacks. This article will explain everything you need to know and suggest relevant security responses.

The hidden threats linked to malicious emails

Countering email security threats demands a calm, methodical approach. Threat management starts with understanding how opening a phishing email can affect your network.

Previously, companies could easily suffer malware infection by opening a suspicious email. Mail clients lacked protection against Javascript attacks, allowing criminals to access user devices directly.

Fortunately, today’s webmail systems are more robust. It’s hard to acquire an email virus simply by opening a message. Virus scanners screen incoming mail before users click, flagging potential threats and avoiding one-click infections.

The bad news is that email security has gone underground. Attackers use subtle methods to persuade users to take risky actions. And they often succeed. Criminals could conceal a malicious payload inside a seemingly innocent email attachment. Or they could redirect readers to unprotected websites.

That’s why we call attachments “hidden threats.” Criminals use deception to create false trust. Targets need to remain vigilant and question every email they receive. Understanding what to look for is critically important.

The most common types of malicious email attachments

Attackers can attach almost any file type to a phishing email. However, not all file types carry the same threat level. Some are harder to detect than others. Let’s run through some common email phishing attacks and explain how they work.

Executable files: The most dangerous attachments

Executable file extensions like .bat, .exe, .com, and .bin are at the top of the email phishing food chain. They should be your top priority when designing email security strategies.

The reason is that executable files automatically launch code when users open them. There are no intermediate steps or additional user actions. Malware executes, embeds itself on the victim’s device, and starts to spread. The user often does not know that the attack is underway.

Executables also routinely evade email security filters, appearing legitimate to casual readers. But one click can lead to severe security consequences.

Infected documents and PDFs

Office documents (such as docx, doc, .xls, or .xlsx) are also attractive vectors for phishing email attacks, but for a slightly different reason. Attackers can seed documents with malicious scripts or macros.

Normally, macros are tools that save time and automate complex processes. However, criminals can use them to execute malware inside applications.

Using documents has some critical advantages. Spreadsheets, PDFs, or Word files are familiar to office workers. Employees might mistake malicious attachments for client contracts, invoices, or strategic documents.

Attackers also improve their chances of success via urgent language. Emails urge recipients to open the document or risk damaging consequences. That’s all superficial. The real consequences materialize after the malicious macro executes.

PDFs play a similar role. In this case, attackers can seed documents with Javascript scripts. However, PDFs have another benefit: attackers can embed links within the PDF attachment, sending targets to fake websites where criminals harvest personal information.

Hidden malware in compressed files

Compressed file formats include .rar and .zip extensions. We commonly use both formats to transfer large files efficiently, but both file formats can become threat vectors.

Compressed files could hold anything. Without opening the file, recipients have no idea whether the content is legitimate or malicious. Intelligent attackers disguise compressed formats as valuable documents or applications, the kind of files targets may need to open. When they do so, the malware executes automatically.

Archives have another benefit: attackers can add password protection. Password protection blocks antivirus software and suggests to victims that the file is authentic – even if that is far from true.

File extension tricks attackers use

Another thing to remember is that appearances are often deceptive when dealing with email attachments. Attackers can use file masking to disguise the nature of attachments and make identifying them harder.

Images and video files are common examples. Recipients may think the attachment is a standard .jpg image. Clever attackers link the image to the target’s personal or professional life. It could be a real estate portfolio or a product listing – at least on the surface. However, a malicious executable lies beneath the surface.

Why deceptive emails fool even careful employees

There are many ways to deceive targets with a phishing email, from PDFs to camouflaged images. But here’s the critical point: any employee can open a suspicious email or download an attachment they should avoid. Nobody is immune. That’s why phishing is such a persistent security issue.

Phishers play on human nature. They mimic legitimate communications from trusted entities, like banks or corporate partners we deal with daily. They prompt rash actions by using an urgent tone and creating false fears. And they use techniques like spoofing and masking to create a veneer of authenticity.

The most sophisticated phishers take these techniques even further. They research their victims and adopt familiar styles of address. They leverage personal information purchased on the Dark Web to profile targets and fine-tune their email content.

Drive-by downloads heighten risks still further. These downloads occur almost invisibly. Victims visit compromised websites via links that appear innocent. No amount of cybersecurity training can prevent infections that occur in the background, without any initial symptoms.

Email security: Preventing hacks and viruses

Hidden threats and devious phishing attacks may seem intimidating but don’t panic. While you could get hacked by clicking a single email, you probably won’t if you adopt email security best practices.

Adopt a strict policy on opening attachments

Treat all email attachments as suspicious by default unless you have requested the file. This policy applies even to attachments from colleagues or trusted partners.

If you receive an unrequested attachment, don’t open it. Ask the sender for verification that the attachment is genuine and what it contains.

Update your PDF reader

PDF attachments are far more dangerous if your reader is out of date. Attackers leverage exploits in older versions while developers plug security gaps with each iteration. Update your reader regularly, preferably as soon as new versions become available.

If possible, upgrade to more secure PDF software. Sophisticated readers include sandboxing to contain potential threats and file validation to screen for malware.

Patch your browser and email client

The same applies to updating your web browser and email application (if you use one). Any web-facing tool may contain exploits or backdoors for malware infection. Regular updates neutralize recently identified vulnerabilities.

Scan emails for viruses and malware

Don’t rely on security tools provided by email services. Scan every incoming attachment with dependable antivirus software that leverages global threat databases. Robust antivirus defenses defend your network edge when other systems fail. Your wider network should remain safe, even if you click on a dangerous file.

Understand how to identify phishing links

Remember: attachments aren’t the only email security threat. Clicking a phishing link can also lead to malware infection or the exposure of personal information. Training employees to avoid fake websites is critically important.

Fake links tend to have convincing anchor text but deceptive URLs. For instance, URLs contain subtle deviations from legitimate versions. Fake websites also tend to contain errors or factual mistakes (such as false tax numbers).

How can NordLayer help

Companies are not alone when dealing with malicious attachments and links. NordLayer’s expertise can help you screen every email before cyber-attacks occur.

Our Download Protection scans every attachment automatically using advanced NordVPN Threat Protection technology. Our solution detects and removes malware instantly before it infects your system. It also gives you an overview of scanned files and allows you to track malicious activity.

Download Protection integrates seamlessly with other NordLayer security tools, adding another essential line of defense.

NordLayer’s Web Protection safeguards your business by blocking access to scam, phishing, and malicious websites. If a user inadvertently clicks on a phishing link, our system will intercept and prevent the connection, protecting your organization from potential security threats.

Ease your email attachment anxiety. Contact the NordLayer team and book a demo to find a security solution for your team.

Frequently asked questions

Can you get a virus from opening an email?

Yes. Malware can execute directly from an email via malicious scripts. However, this is unlikely with proper security measures. Infection via attachments and malicious links is much more common.

Is it safe to reply to an unknown email?

Yes, but you should always exercise caution. Phishers may engage you in conversation to build trust and deliver malware. Ask senders to verify their identities before proceeding. If they cannot do this, end the conversation and report the phishing email.

Never open attachments from unknown senders, and avoid following links in emails from strange contacts. Always ask who has sent the message, what they want, and whether they are who they claim to be.

What to do if you click on a phishing link?

Firstly, don’t panic. If a download prompt appears, decline the transfer. Don’t interact with any forms or links on the phishing website. Leave the site as quickly as possible.

To be safe, disconnect your device from the internet and run a system scan. You may want to change critical passwords (a good security practice anyway). And report the fake website to Google.