Rewterz Threat Alert – Heatstroke Phishing Campaign

Wednesday, September 11, 2019



Analysis Summary

A new multistage phishing attack dubbed “Heatstroke” and how it may differ from other phishing campaigns. The attackers apparently do research on their potential victims and instead of targeting their work email addresses, the victim’s private email addresses are targeted. Trend Micro indicated that these may have come from the victim’s own address list. Personal email addresses are more likely to be hosted on free email providers and may have a more lax security configuration than an organization’s mail servers. Thus the phishing emails are more likely to reach their target. If for instance, a Gmail victim falls prey to their scheme, the attackers may gain access not only to the victim’s email account, but potentially their Google Drive and associated Android devices as well. The landing page presented to the victim, should they follow the link provided in the phishing email, presents a multi-page website, where the credentials are not requested immediately. The victim has to traverse a few pages before the credential request is shown. This could potentially be an attempt to lull the victim into thinking this is a legitimate site. The landing page is written in PHP and has the ability to return a 404 (not found error code) should the victim be connecting in from a country, domain or IP address, the attackers have black listed. The attack is based on a phishing kit that is offered as a service. Trend Micro indicated that they saw another group purchase the kit while they were doing research on Heatstroke. The stolen credentials are sent back to the attackers, via email, with the data hidden using steganography techniques.


Credential theft

Indicators of Compromise



Malware Hash (MD5/SHA1/SH256)



  • Block all threat indicators at your respective controls.
  • Always be suspicious about emails sent by unknown senders.
  • Never click on the link/attachments sent by unknown senders.

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