Nifty.com Used as Phishing Infrastructure: How Raven Detected Abuse of Trusted Infrastructure

Between April- May 2025, Raven uncovered a sophisticated phishing campaign that didn’t spoof a trusted domain — it used one.

A multi-wave phishing campaign abused legitimate Nifty.com infrastructure to impersonate trusted business workflows and harvest credentials. Raven detected the attack despite clean headers, valid authentication, and no obvious red flags.

​Editors note: The same blog is available in Japanese here​

A Campaign Built for Evasion

The attackers didn’t spoof a domain — they used it legitimately.

They registered free accounts on nifty.com, a well-known Japanese ISP, and launched phishing emails directly from its infrastructure. Because these were real accounts, all authentication layers passed:

This alone allowed them to bypass most secure email gateways (SEGs) that rely heavily on these checks.

Campaign Timeline: Multiple Waves, Adaptive Behaviour

The repetition and timing suggest automation and possible kit-based orchestration.

Anatomy of the Campaign

1. Infrastructure Used

• Domain: nifty[.]com (legitimate Japanese ISP)

• Mail Servers: mta-snd-e0X.mail.nifty[.]com

• IP Ranges: 106.153.226.0/24, 106.153.227.0/24

• Sender Accounts: Free consumer addresses impersonating businesses

2. Payload and Delivery Method

• No links in the email body

• Malicious attachments:

  • File types: .pdf and .html

  • Filenames like: SAFE_Terms_May2025.pdf, Execution_Agreement.html

• Redirect chain (sanitized):

  • clickme[.]thryv[.]com → benign-looking marketing tracker

  • 2vf78gnafutdc5zqmhng[.]iqmwpx[.]ru → phishing site with obfuscated JavaScript

  • Embedded email in URL fragment for tracking (e.g., #[email protected])

3. Techniques Designed to Evade Detection

• HTML padding: Use of whitespace characters (=20,  ) to bypass filters

• Multipart MIME structure: Payloads hidden in attachments

• Display name spoofing: Examples like “Name via DocuSign” to imply legitimacy

• Obfuscated links: Redirectors that aren't obvious bad URLs

• Flawless grammar and tone: Indicative of AI-generated or phishing kit templates

4. Behavioural Indicators Flagged by Raven

• Unusual sender-recipient combinations

• Repeated use of contract-related lures across recipients

• Brand impersonation in display names

• Identical attachment patterns across campaigns

• Obfuscated redirect chains leading to flagged infrastructure

Threat Classification

• Vector: Abuse of authenticated Nifty.com mail infrastructure

• Attack Type: Redirect-based phishing delivered via file attachments

• Intent: Credential harvesting, including Gmail session/token theft

• Sophistication Level: Medium to High — use of evasive techniques and infrastructure blending

• Attribution Signals: Likely use of phishing kits, with signs of automation or AI-generated content

Why Most Defenses Missed It

Legacy email security often relies on:

• Broken SPF/DKIM

• Blacklisted domains

• Suspicious URLs in body

• Behavioral triggers from mail headers

This campaign had none of those.

What Raven Recommends

Defending against this class of attack requires going beyond basic hygiene:

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