The use of embedded HTML documents in phishing e-mails is a standard technique employed by cybercriminals. It does away with the need to put links in the e-mail body, which antispam engines and e-mail antiviruses usually detect with ease. HTML offers more possibilities than e-mail for camouflaging phishing content.
There are two main types of HTML attachments that cybercriminals use: HTML files with a link to a fake website or a full-fledged phishing page. In the first case, the attackers can not only hide a link in the file, but also automatically redirect the user to the fraudulent site when they open this file. The second type of HTML attachment makes it possible to skip creating the website altogether and save on hosting costs: the phishing form and the script that harvests the data are embedded directly in the attachment. In addition, an HTML file, like an e-mail, can be modified according to the intended victim and attack vector, allowing for more personalized phishing content.