How To Avoid Cyberattacks Via Excel Add-Ins?

There are more than two thousand Excel add-ins on the market right now. They help people increase the functionality of Excel applications and get more out of them. By using Excel add-ins, you can automate tasks such as business analysis, accounting, or charting. These were usually manual tasks that take a considerable amount of time, but not anymore.

But recent reports about Excel add-ins are incredibly concerning. According to the Journal of Accountancy, Excel add-in-related cyberattacks increased by almost 600%. This means that businesses that use these tools are at a high risk of compromising the valuable data they have on their sheets. Since we know how big is the threat, it is time to understand how to avoid cyberattacks via Excel add-ins.

Excel Add-Ins

Excel add-ins are files that have the .xll extension, these can be utilized to increase the productivity and functionality of Excel. Although these are mostly used by accountants, Excel add-ins can manage a variety of tasks such as reading through the texts, writing data, and conducting calculations. One of the best parts of these tools is the ability to automate these boring tasks and spend your time on more important, creative things.

Most people who know how to code can usually write these add-ins on their own, but there are also ready-to-use add-ins on the market. This is where the real threat begins as they can take possession of a great deal of sensitive information when implemented into Excel applications. Especially in recent years, .xll extensions became one of the prominent ways for cybercriminals to access unauthorized data.

How to Avoid Excel Add-In Cyberattacks>

Attacks emerging from the .xll extension put company data at risk along with valuable client information. When you consider that add-ins are popular tools amount accounting departments, you can imagine how detrimental these attacks can be. Ransom, downtime, data loss, and other business-threatening risks are associated with these attacks. Let’s see how to avoid them effectively.

1-) Use Trust Center to Allow Trusted Publishers

Add-ins from unknown sources are a way to keep the door open to cybercriminals. If you don’t have a list of trusted add-in publishers and any kind of .xll can be executed in your systems, you are basically inviting data thieves to compromise your network.

Well luckily, Excel has a great feature called the “Trust Center”. This tool allows you to configure Excel to only allow add-ins from trusted publishers and avoid the others. You can control file types, publishers, trusted locations, and much more from this simple tool. It is also possible to block ​​proprietary add-ins with this tool since they can be dangerous and lack transparency.

2-) Use Identity and Access Management (IAM)

One of the prominent risks associated with Excel add-ins is the permissions granted to the tool and the scope of resources they can access with these permissions. Although some of these attacks might only cause some downtime, they can go up to compromise a significant part of the resources.

One of the best ways to control access permissions and prevent unauthorized access is by using Identity and Access Management (IAM) solutions. Since the prominent issue with add-ins is the concern of how much permission they have, managing access levels proves to be an effective way to prevent these attacks.

IAM solutions allow companies to decide the access levels of every end user, and they go above and beyond to ensure that correct verification tools are in place to authenticate these users. Since IAM constantly monitors user access levels and verification, you can monitor what the users are doing in your network with full details. This protection greatly decreases the risk of .xll files compromising your network. To understand the in-depth benefits of IAM, visit here.

3-) Configure Email Gateways

Another way that Excel add-ins penetrate a network and compromise its resources is through phishing emails. Attackers use ways such as email thread hijacking and attaching malicious .xll files to phishing emails. Then the end user clicks on the file without idea of how dangerous it is, and the .xll file injects malware or ransomware.

Effective ways of decreasing the risk of phishing attacks through .xll files are first training your employees on phishing attacks and making them aware of how to avoid these emails. But more importantly, you need to have your IT security team configure email gateways to block .xll attachments to avoid the risk altogether. By configuring your email gateways, you will have the ability to only allow add-ins through trusted publishers and minimize the risk of phishing attacks.

4-) Use Content Filtering

Content filtering is a great tool to prevent suspicious content and emails that your employees are exposed to on a daily basis. You might configure this by creating allowlists or blocklists through firewalls and such, but new threats are emerging every day. This means that effective filtering through traditional methods is not possible.

Content filtering solutions allow companies to dynamically filter incoming content and email, and block unfriendly websites. They are dynamic because these tools constantly monitor the web traffic, and when implemented, they act like a security guard over the network.

Using a content filtering solution will help you minimize .xll attacks through emails and other forms of online content. They will significantly decrease the risk of being infected with malware through these add-in attacks and will make sure that malicious .xll files are not ending up in the users’ inboxes.


Excel add-ins are great tools that make life easier for people who work on Excel sheets. They are capable of reducing the manual labor on repetitive tasks and automating things like reading data and conducting business analysis. Many people can now get these add-ins through .xll files and implement them in their systems.

However, Excel add-ins are now one of the biggest sources of malware and data theft. Since they are granted considerable access permissions, malicious .xll files pose the risk of compromising private networks and stealing sensitive data. If you want to be safe using these tools, make sure to consider the solutions above.

Priyanka is an entrepreneur & content marketing expert. She writes tech blogs and has expertise in MS Office, Excel, and other tech subjects. Her distinctive art of presenting tech information in the easy-to-understand language is very impressive. When not writing, she loves unplanned travels.