Apple’s latest operating system update, iOS 26, inadvertently introduces a forensic disaster for security researchers and device users concerned about spyware infections.
The update fundamentally changes how the shutdown.log file works, effectively erasing crucial evidence of sophisticated malware such as Pegasus and Predator spyware from affected devices.
For years, the shutdown.log file buried in the Sysdiagnoses section of Unified Logs served as a critical forensic artifact for detecting iOS malware.
Located in the Sysdiagnose Folder > system_logs.logarchive > Extra > shutdown.log path, this log file records system activities during the device shutdown sequence, providing investigators with an often-overlooked window into potential compromises.
However, iOS 26 fundamentally changes this by overwriting the shutdown.log file every time the device restarts rather than adding new entries and retaining historical snapshots.
iOS 26 Shutdown.log change: a critical vulnerability
The move from append to overwrite represents either an intentional design decision or an unforeseen bug with significant implications.
When users update to iOS 26 and then restart their devices, all previous entries in the shutdown.log file are completely erased, destroying any evidence of past Pegasus or Predator infections.
This automatic disinfection of forensic artifacts occurs at precisely the wrong time, as spyware attacks continue to target high-level leaders, celebrities and civil society figures globally.
The technical mechanism is simple but devastating: instead of keeping a historical log file that grows with each shutdown event, iOS 26 replaces the entire shutdown.log file with new entries. Any indicators of compromise previously recorded in old log entries are permanently lost.
This development particularly affects users who may have been unknowingly infected for long periods of time, as their forensic trail is completely destroyed during the update.
Implications for malware detection and forensic investigations
Prior to iOS 26, security researchers identified specific indicators of compromise related to anomalies in shutdown.log.
Pegasus 2022 infections, for example, left traces of /private/var/db/com.apple.xpc.roleaccountd.staging/com.apple.WebKit.Networking entries in the log, revealing NSO Group’s transition to using legitimate system process names rather than obviously suspicious identifiers.
Additionally, investigators using containermanagerd log correlation on iOS 18 and earlier devices were able to identify discrepancies between startup events and shutdown.log entries, revealing hidden malicious activity.
With iOS 26 automatically eliminating this forensic evidence, compromised devices become virtually indistinguishable from clean systems, leaving no external evidence or real-time detection mechanisms.
Users concerned about a potential compromise should immediately extract and maintain a system diagnostic of their device before updating to iOS 26, protecting any historical shutdown.log data that may reveal infections.
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