The email messages used to deliver phishing-trojans are typically designed to look like normal business communications, often related to taxes, invoicing, deliveries, salaries or other work-related matters. They may also use the branding or names of legitimate companies to further the impression of authenticity. Such messages are also known as phishing emails.
The attached files are most frequently Microsoft Office documents (Word, Excel, etc), though PDF, HTML or ZIP files are also common. The files usually use fairly innocuous file names, such as 'Invoice', or 'Delivery statement'. to give the impression that they are legitimate.
The careful crafting of the email message and file attachments to appear authentic are all examples of social engineering.
Decoy documents and enabling macros
If the user opens the file, most will also display an authentic-looking document as a decoy, to distract the user from any unauthorized actions that occur in the background.
If the file is a Microsoft Office document, and the user's Office settings disable macros by default, a notification message may be displayed asking the user to enable macros, supposedly so that they can view the document contents correctly. In reality, doing so would allow the malicious code embedded in the document to run and install malware on the device.
If the attached file is opened, code embedded in it will run and either:
- Drop a malicious component or program contained in the file onto the device and install it OR
- Contact a remote server and download a malicious component or program from the server onto the device
The specific harmful program installed onto the device varies, and may be separately detected by security products.