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Attackers Season Spam With a Touch of 'Salt' to Bypass Microsoft 365 and Google Workspace Email Security
- Rescana
- Oct 8
- 5 min read
Executive Summary
The "Attackers Season Spam With a Touch of 'Salt'" campaign represents a sophisticated evolution in spam and phishing operations, leveraging advanced obfuscation techniques to bypass traditional email security controls. First reported by Dark Reading and subsequently amplified by leading cybersecurity news outlets and social media channels, this campaign utilizes "salted" or randomized content within spam emails, making detection and mitigation significantly more challenging for organizations. The campaign is notable for its use of hidden content, dynamic email headers, and the exploitation of legitimate web resources to increase the likelihood of successful delivery and user engagement. While no specific indicators of compromise (IOCs) or targeted vulnerabilities have been published in open sources, the tactics, techniques, and procedures (TTPs) observed align with those used by both financially motivated cybercriminals and advanced persistent threat (APT) actors. This advisory provides a comprehensive technical analysis of the campaign, its threat actor profile, exploitation methods, victimology, and actionable mitigation strategies to help organizations defend against this emerging threat.
Threat Actor Profile
Based on the available open-source intelligence, the "Attackers Season Spam With a Touch of 'Salt'" campaign has not been directly attributed to a specific threat actor or APT group. The operational sophistication, including the use of obfuscation and hidden content, suggests a high level of technical capability consistent with both organized cybercriminal groups and state-sponsored actors. The campaign's broad targeting and reliance on generic spam and phishing vectors indicate a financially motivated objective, although the techniques employed are also consistent with those used in credential harvesting and initial access operations by APTs. The lack of direct attribution in public reporting underscores the importance of monitoring for evolving TTPs rather than focusing solely on known threat actor signatures.
Technical Analysis of Malware/TTPs
The technical core of the "Attackers Season Spam With a Touch of 'Salt'" campaign lies in its innovative use of "salt"—a term borrowed from cryptography, here referring to the randomization and obfuscation of email content and metadata. This approach is designed to defeat static and heuristic-based spam filters, which often rely on pattern recognition and signature matching.
The campaign leverages several advanced TTPs, including the insertion of random strings or characters into email headers, subject lines, and message bodies. This "salting" process ensures that each email instance is unique, significantly reducing the efficacy of traditional detection mechanisms. Additionally, the use of hidden content—such as invisible HTML elements, zero-width characters, or base64-encoded payloads—further complicates analysis and detection by both automated systems and human analysts.
Attackers are also exploiting legitimate web applications and resources, such as Can I email and other email testing or validation platforms, to increase the deliverability and credibility of their messages. By embedding links to reputable domains or mimicking the formatting of legitimate communications, the campaign increases the likelihood of user interaction and successful compromise.
From a MITRE ATT&CK perspective, the campaign aligns with the following techniques: T1566.001 (Phishing: Spearphishing Attachment), T1566.002 (Phishing: Spearphishing Link), and T1204 (User Execution). The use of obfuscated and salted content is a direct countermeasure to common email security controls, including those provided by Microsoft Exchange Online Protection, Proofpoint, and Mimecast.
No specific malware families or payloads have been identified in the public reporting; however, the campaign's primary objective appears to be credential harvesting, malware delivery, or the establishment of initial access for follow-on operations.
Exploitation in the Wild
While no confirmed breaches or exploitation incidents have been publicly attributed to the "Attackers Season Spam With a Touch of 'Salt'" campaign, the widespread amplification of the campaign by reputable cybersecurity news outlets and social media channels indicates active exploitation in the wild. The campaign's reliance on generic spam and phishing vectors suggests a broad targeting strategy, with potential victims spanning multiple sectors and geographies.
The use of obfuscated and salted content has been observed to successfully bypass both on-premises and cloud-based email security solutions, resulting in increased delivery rates and user exposure. Organizations should be particularly vigilant for emails containing unusual or randomized elements, hidden content, or links to legitimate but unexpected web resources.
Victimology and Targeting
The campaign appears to be opportunistic in nature, targeting a wide range of organizations and individuals rather than focusing on a specific sector or geography. The use of generic spam and phishing lures, combined with advanced obfuscation techniques, increases the likelihood of successful compromise across diverse environments.
Potential victims include enterprises using popular email platforms such as Microsoft 365, Google Workspace, and Zimbra, as well as individuals with personal email accounts. The campaign's use of legitimate web resources and dynamic content further broadens its potential impact, making it a significant threat to organizations of all sizes and industries.
Mitigation and Countermeasures
To defend against the "Attackers Season Spam With a Touch of 'Salt'" campaign, organizations should implement a multi-layered email security strategy that goes beyond traditional signature-based detection. Key recommendations include:
Enhancing email filtering rules to detect and quarantine messages containing obfuscated or randomized content, such as unusual character strings, hidden HTML elements, or base64-encoded payloads. Security teams should regularly review and update these rules to account for emerging obfuscation techniques.
Deploying advanced threat protection solutions that leverage machine learning and behavioral analysis to identify anomalous email patterns and user interactions. Solutions from vendors such as Microsoft Defender for Office 365, Proofpoint Targeted Attack Protection, and Mimecast Threat Protection offer capabilities to detect and block sophisticated phishing and spam campaigns.
Conducting regular user awareness training to educate employees about the risks associated with advanced phishing and spam tactics. Training should emphasize the importance of scrutinizing unexpected emails, avoiding interaction with suspicious links or attachments, and reporting potential threats to the security team.
Implementing robust incident response procedures to rapidly identify, contain, and remediate email-based threats. This includes monitoring for indicators of compromise, conducting forensic analysis of suspicious emails, and coordinating with external threat intelligence providers for timely updates on emerging campaigns.
Maintaining up-to-date threat intelligence feeds and monitoring reputable sources such as Dark Reading, TheCyberSecHub, and TokyoBlackHatNews for the latest information on evolving spam and phishing campaigns.
References
About Rescana
Rescana is a leader in third-party risk management (TPRM), providing organizations with a comprehensive platform to assess, monitor, and mitigate cyber risks across their extended supply chain. Our platform leverages advanced analytics, continuous monitoring, and actionable intelligence to empower security teams to proactively manage vendor risk and enhance organizational resilience. For more information about how Rescana can help your organization strengthen its cyber defense posture, we invite you to contact us at ops@rescana.com. We are happy to answer any questions you may have.
