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Summary
In the summer of 2020, there was a big, short-lived spike in malicious Office documents. The Emotet crew had been quiet in the spring and began leveraging their botnet to send extremely convincing phishing emails to their victims, often with a link to download an invoice or other document from a popular cloud service. Those documents contained malicious code that installed backdoors, ransomware, bankers, and other malware on unsuspecting victims’ computers. This blog post looks back at malicious Office document trends in 2020, with a preview of what is to come in 2021.
This blog post accompanies the release of the February 2021 Cloud and Threat Report, which analyzes 2020’s most interesting trends in enterprise cloud and web security. In addition to highlighting the increase in cloud app usage, the Cloud Threat Report also highlights four other noteworthy trends from 2020:
- Cloud app use continues to rise, with a 20% increase led by collaboration and consumer apps
- Cloud-delivered malware continues to increase, now representing 61% of all malware.
- Cloud phishing continues to increase, with 13% of phishing campaigns hosted in the cloud and 33% targeting cloud app credentials.
- Personal app usage in the enterprise continues to increase, with 83% of users accessing personal apps from managed devices.
The calm
The February 2021 Cloud and Threat Report examines trends in malicious Office documents at a quarterly granularity. In this blog post, we take a more granular look at a broader dataset. The chart below shows the percentage of malware downloads detected by the Netskope Security Cloud Platform that were Office documents. For the first three months of the year, Office documents represented nearly 20% of all malware downloads. This changed in April and May, in the early days of the COVID-19 pandemic, when the Emotet crew and other threat actors were relatively quiet. During that time, only 10% of malware downloads were Office documents.
Throughout the year, the Office document format most favored by cybercriminals was the Excel spreadsheet, representing 61.1% of all the malicious office documents in 2020. Excel is most popular because it provides rich scripting capabilities that threat actors abuse for malicious purposes. Word documents were the second most popular, followed by a small selection of Powerpoint documents.
