Detect Malvertising in CrowdStrike LogScale
Adversaries may purchase online advertisements to distribute malware to victims. Ads can be positioned prominently in search results or on popular websites, exploiting user trust in those platforms. Malvertising campaigns frequently spoof legitimate software vendors, tricking users into downloading trojanized installer packages. Because the adversary's infrastructure purchase occurs entirely outside the victim environment, detection must pivot to observable victim-side indicators: browsers spawning unexpected child processes, executable file downloads staged in user-writable directories, and drive-by script execution patterns consistent with clicking a malicious ad.
MITRE ATT&CK
- Tactic
- Resource Development
- Technique
- T1583 Acquire Infrastructure
- Sub-technique
- T1583.008 Malvertising
- Canonical reference
- https://attack.mitre.org/techniques/T1583/008/
LogScale Detection Query
#event_simpleName=ProcessRollup2
| ParentBaseFileName = /(?i)^(chrome|msedge|firefox|iexplore|opera|brave|safari)\.exe$/
| FileName = /(?i)^(powershell|pwsh|cmd|mshta|wscript|cscript|rundll32|regsvr32|msiexec|certutil|bitsadmin)\.exe$/
| DownloadPath := if(CommandLine = /(?i)(\\Downloads\\|\\Temp\\|AppData\\Local\\Temp)/, 1, 0)
| NetworkRef := if(CommandLine = /(?i)(http:\/\/|https:\/\/|ftp:\/\/)/, 1, 0)
| EncodedOrDL := if(CommandLine = /(?i)(-enc|-encodedcommand|\biex\b|downloadstring|downloadfile|webclient|invoke-webrequest)/, 1, 0)
| HiddenOrSilent := if(CommandLine = /(?i)(-windowstyle\s+hidden|-w\s+hidden|\/quiet|\/silent|\/verysilent)/, 1, 0)
| SuspicionScore := DownloadPath + NetworkRef + EncodedOrDL + HiddenOrSilent + 1
| select([@timestamp, ComputerName, UserName, ParentBaseFileName, FileName, CommandLine, DownloadPath, NetworkRef, EncodedOrDL, HiddenOrSilent, SuspicionScore])
| sort(SuspicionScore, order=desc)CrowdStrike LogScale (Falcon) query against ProcessRollup2 events to detect malvertising-driven browser-to-child-process execution chains. Parent process is filtered to known browser executables; child process to LOLBins and interpreters commonly abused post-ad-click. Four inline computed fields score risk factors matching the reference KQL/SPL logic (download path, network URL, encoded/download commands, hidden execution), with the total suspicion score used to rank events for analyst review.
Data Sources
Required Tables
False Positives & Tuning
- Falcon-managed hosts running Citrix Workspace or VMware Horizon web clients that present a browser UI and internally spawn msiexec.exe or powershell.exe for plugin or agent updates, including silent-install flags.
- Corporate software distribution portals where employees click download links in Edge/Chrome that directly invoke the installer (msiexec.exe /quiet) from the Downloads folder, matching all scored indicators without malicious intent.
- Security operations tooling (e.g., Velociraptor web console, Splunk SOAR browser triggers) that invoke powershell.exe or cmd.exe via browser-based action buttons, producing high-scoring events from a trusted workflow.
Other platforms for T1583.008
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate Browser Spawning PowerShell (Malvertising Drive-by Pattern)
Expected signal: Sysmon Event ID 1: Process Create with Image=powershell.exe, ParentImage=cmd.exe, CommandLine containing '-WindowStyle Hidden'. Sysmon Event ID 11: File Create for malv-test.txt in Temp. Security Event ID 4688 (if command line auditing enabled). PowerShell ScriptBlock Log Event ID 4104 showing Write-Output command.
- Test 2Stage and Execute Trojanized Installer from Downloads Folder
Expected signal: Sysmon Event ID 11: File Create for 7zip-2400-x64.exe in the Downloads folder. Sysmon Event ID 1: Process Create with Image path inside the Downloads folder — anomalous for any legitimate software. Security Event ID 4688 if command line auditing is enabled.
- Test 3HTA Drive-by Execution Simulating Malvertising Redirect
Expected signal: Sysmon Event ID 1: Process Create for mshta.exe with TargetFilename in Temp path. Sysmon Event ID 11: File Create for hta-atomic.txt. Security Event ID 4688 for mshta.exe execution. If launched from a browser parent, the main detection fires on mshta.exe as a SuspiciousChild with DownloadPath=1.
- Test 4PowerShell Download Cradle Spawned from Browser Context (Simulated Raspberry Robin Pattern)
Expected signal: Sysmon Event ID 1: Process Create for powershell.exe, ParentImage=cmd.exe, CommandLine containing 'Net.WebClient' and 'DownloadString'. Sysmon Event ID 3: Network connection attempt to 127.0.0.1:18080 (connection refused, but event still fires). PowerShell ScriptBlock Log Event ID 4104 showing the download cradle code.
References (7)
- https://attack.mitre.org/techniques/T1583/008/
- https://www.spamhaus.com/resource-center/a-surge-of-malvertising-across-google-ads-is-distributing-dangerous-malware/
- https://labs.guard.io/masquerads-googles-ad-words-massively-abused-by-threat-actors-targeting-organizations-gpus-42ae73ee8a1e
- https://www.ic3.gov/Media/Y2022/PSA221221
- https://www.sentinelone.com/blog/breaking-down-the-seo-poisoning-attack-how-attackers-are-hijacking-search-results/
- https://www.bbc.com/news/technology-12891182
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1583.008/T1583.008.md
Unlock Pro Content
Get the full detection package for T1583.008 including response playbook, investigation guide, and atomic red team tests.