Among the developments that have disturbed security teams around the world, threat-intelligence analysts have detected a sudden and unusually coordinated wave of probing of Palo Alto Networks' GlobalProtect remote access infrastructure. This activity appears to be influenced by the presence of well-known malicious fingerprints and well-worn attack mechanisms.

It has been revealed in new reports from GreyNoise that the surge began on November 14 and escalated sharply until early December, culminating in more than 7,000 unique IP addresses trying to log into GlobalProtect portals through the firm's Global Observation Grid monitored by GlobalProtect. This influx of hostile activity has grown to the highest level in 90 days and has prompted fresh concerns among those defending the computer system from attempts to hack themselves, who are watching for signs that such reconnaissance is likely to lead to a significant breach of their system. 

In general, the activity stems mostly from infrastructure that operates under the name 3xK GmbH (AS200373), which accounts for approximately 2.3 million sessions which were directed to the global-protect/login.esp endpoint used by Palo Alto's PAN-OS and GlobalProtect products. The data was reported by GreyNoise to reveal that 62 percent of the traffic was geolocated in Germany, with 15 percent being traced to Canada. 

In parallel, AS208885 contributed a steady stream of probing throughout the entire network. As a result of early analysis, it is clear that this campaign requires continuity with prior malicious campaigns that targeted Palo Alto equipment, showing that recurring TCP patterns were used, repeated JA4T signatures were seen, and that infrastructure associated with known threat actors was reused. 

Despite the fact that the scans were conducted mainly in the United States, Mexico, and Pakistan regions, all of them were subjected to a comparable level of pressure, which suggested a broad, opportunistic approach as opposed to a narrowly targeted campaign, and served as a stark reminder of the persistent attention adversaries pay to remote-access technologies that are widely deployed. 

There has been a recent increase in the activity of this campaign, which is closely related to the pattern that was first observed between late September and mid-October, when three distinct fingerprints were detected among more than nine million nonspoofable HTTP sessions, primarily directed towards GlobalProtect portals, in an effort to track the attacks. 

There is enough technical overlap between four autonomous systems that originate those earlier scans to raise early suspicion, even though they had no prior history of malicious behavior. At the end of November, however, the same signatures resurfaced from 3xK Tech GmbH’s infrastructure in a concentrated burst. This event generated about 2.3 million sessions using identical TCP and JA4t indicators, with the majority of the traffic coming from IP addresses located in Germany. 

In the present, GreyNoise is highly confident that both phases of activity are associated with a single threat actor. It has now been reported that fingerprints of the attackers have reapplied on December 3, this time in probing attempts against SonicWall's SonicOS API, suggesting more than a product-specific reconnaissance campaign, but a more general reconnaissance sweep across widely deployed perimeter technologies. According to security analysts, GlobalProtect remains a high-profile target because of its deep penetration into enterprise networks and its history of high-impact vulnerabilities. 

It is important to note, however, that CVE-2024-3400 is still affecting unremedied systems despite being patched in April 2024 with a 9.8 rating due to a critical command-injection flaw, CVE-2024-3400. During recent attacks, malicious actors have used pre-authentication access as a tool for enumerating endpoints, brute-forcing credentials, and deploying malware to persist by exploiting misconfigurations that allow pre-authentication access, such as exposed administrative portals and unchanged default credentials. 

They have also developed custom tools modeled on well-known exploitation frameworks. Although researchers caution that no definitive attribution has been established for the current surge of activity, Mandiant has observed the same methods being used by Chinese state-related groups like UNC4841 in operations linked to those groups. A number of indicators of confirmed intrusions have included sudden spikes in UDP traffic to port 4501, followed by HTTP requests to "/global-protect/login.urd," from which attackers have harvested session tokens and gotten deeper into victim environments by harvesting session tokens.

According to a Palo Alto Networks advisory dated December 5, administrators are urged to harden exposed portals with multi-factor authentication, tighten firewall restrictions, and install all outstanding patches, but noted that properly configured deployments remain resilient despite the increased scrutiny. Since then, CISA has made it clear that appropriate indicators have been added to its Catalog of Known Exploited Vulnerabilities and that federal agencies must fix any issues within 72 hours. 

The latest surge in malicious attacks represents a stark reminder of how quickly opportunistic reconnaissance can escalate into compromise when foundational controls are neglected, so organizations should prepare for the possibility of follow-on attacks. Security experts have highlighted that these recent incidents serve as a warning to organizations about potential follow-on attacks. A number of security experts advise organizations to adopt a more disciplined hardening strategy rather than rely on reactive patching, which includes monitoring the attack surface continuously, checking identity policies regularly, and segmenting all remote access paths as strictly as possible. 

According to analysts, defenders could also benefit from closer alignment between security operations teams and network administrators in order to keep an eye on anomalous traffic spikes or repeated fingerprint patterns and escalate them before they become operationally relevant. Researchers demonstrate the importance of sharing indicators early and widely, particularly among organizations that operate internet-facing VPN frameworks, as attackers have become increasingly adept at recycling infrastructure, tooling, and products across many different product families. 

Even though GlobalProtect and similar platforms are generally secure if they are configured correctly, recent scan activity highlights a broader truth that is not obvious. In order to remain resilient to adversaries who are intent on exploiting even the slightest crack in perimeter defenses, sustained vigilance, timely remediation, and a culture of proactive security hygiene remain the most effective barriers.