XCSSET collects contacts and application data from files in Desktop, Documents, Downloads, Dropbox, and WeChat folders.4
tool
XCSSET S0658
- Type
- malware
- Platform
- macOS
- Created
- 5 October 2021
- Last modified
- 4 April 2025
XCSSET is a modular macOS malware family delivered through infected Xcode projects and executed when the project is compiled. Active since August 2020, it has been observed installing backdoors, spoofed browsers, collecting data, and encrypting user files. It is composed of SHC-compiled shell scripts and run-only AppleScripts, often hiding in apps that mimic system tools (such as Xcode, Mail, or Notes) or use familiar icons (like Launchpad) to avoid detection.[1][2][3]
33
TechniquesTop 6%
12
TacticsTop 1%
0
Threat groupsNone recorded
0
CampaignsNone recorded
Enterprise ATT&CK only. Any Mobile or ICS rows on the same ATT&CK page are not carried.
MITRE reference S0658
Older XCSSET variants use xxd to encode modules. Later versions pass an xxd or base64 encoded blob through multiple decoding stages to reconstruct the module name, AppleScript, or shell command. For example, the initial network request uses three layers of hex decoding before executing a curl command in a shell.5
XCSSET installs malicious application bundles that mimic native macOS apps, such as Safari, by using the legitimate app’s icon and customizing the Info.plist to match expected metadata.67
XCSSET retrieves files that match the pattern defined in the INAME_QUERY variable within the user's home directory, such as *test.txt, and are below a specific size limit. It then archives the files and exfiltrates the data over its C2 channel.89
XCSSET prompts the user to input credentials using a native macOS dialog box leveraging the system process /Applications/Safari.app/Contents/MacOS/SafariForWebKitDevelopment.10
XCSSET uses a shell script to execute Mach-o files and osacompile commands such as, osacompile -x -o xcode.app main.applescript.11
Standing S0658
Reach is how much of ATT&CK this tool touches. Coverage is how well defended each thing it does is, as a median per technique rather than a total — a total would just restate the reach. Each figure is ranked against all 825 ATT&CK software entries only where that population actually spreads. Where most of the population shares one value, a percentile would rank the tie instead of the entity, so the raw value is shown and no rank is claimed.
Reach
Techniques33Top 6%
94th percentile · 94% of 825 ATT&CK software entries have this many Enterprise techniques or fewer.
Tactics12Top 1%
100th percentile · None of the 825 ATT&CK software entries has more tactics spanned — the highest in the population.
Threat groups061% tie · 22 values
61% of the population shares a single value across only 22 distinct values, so a percentile here would rank the tie, not the entity.
Campaigns085% tie · 8 values
85% of the population shares a single value across only 8 distinct values, so a percentile here would rank the tie, not the entity.
Coverage
Rules / technique7medBottom 9%
9th percentile · 91% of 825 ATT&CK software entries have more detection rules per technique.
Tests / technique3med
Detection coverage S0658
560 distinct rules cover the 33 techniques recorded for this tool. The 585 technique-to-rule mappings resolve to 560 distinct rules, because one rule can cover several techniques. 352 Sigma · 208 Splunk.
31 covered by at least one rule2 with no coverage560 distinct rules in total
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