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Introduction:
A sophisticated software supply chain attack is unfolding in the .NET ecosystem as a malicious NuGet package masquerading as the official Braintree payment gateway client was published on July 3, 2026. Socket’s AI-driven automation flagged the typosquat package as potential malware within ten minutes of its release, but not before it had already begun targeting developers who mistakenly integrate it into production applications. This multi-stage .NET implant is designed to intercept live payment card data, exfiltrate Braintree merchant API keys, and harvest host environment secrets upon assembly load, representing one of the most dangerous supply chain threats to payment processing systems in recent memory.
Learning Objectives:
- Understand the mechanics of typosquatting attacks in the NuGet ecosystem and how attackers exploit naming conventions and fake download statistics
- Identify the multi-stage infection chain, including the companion dependency `DependencyInjector.Core` and XOR-obfuscated C2 infrastructure
- Implement practical detection, mitigation, and remediation strategies including Linux/Windows commands, dependency scanning, and egress monitoring
- Learn how to verify package authenticity, audit NuGet dependencies, and secure payment gateway credentials against exfiltration
You Should Know:
1. Anatomy of the Braintree.Net Typosquat Attack
The malicious package `Braintree.Net` is a carefully crafted impersonation of PayPal’s legitimate Braintree .NET SDK, which is published on NuGet under the official ID `Braintree` and maintained in the 5.x line. Attackers exploited a common naming variation — adding “.Net” to the package name — to deceive developers searching for “Braintree .NET” or copying installation commands from unofficial sources.
The deception extends beyond naming. The malicious package ships real-looking `Braintree.dll` assemblies for multiple target frameworks including net452, netstandard2.0, net8.0, net9.0, and net10.0. It uses a mismatched version scheme (3.36.1 versus the official 5.x), and its metadata points to the legitimate `braintree/braintree_dotnet` GitHub repository, creating a convincing facade. The claimed author is listed as “Braintree,” impersonating the official `braintreepayments` profile.
To further inflate its perceived legitimacy, attackers published over 120 empty placeholder versions (0.0.1 through 0.0.120) in a single day, each containing only a `.nuspec` file with no DLL. This namespace-squatting technique artificially boosted the total download count to approximately 14 million, with roughly 11 million being padding sprayed across throwaway versions. In reality, the genuinely malicious releases (3.35.8 through 3.36.1) have only approximately 334 real installs — a staggering 32,900x gap between the headline number and the actual blast radius.
Detection Commands:
Linux/macOS (checking NuGet packages in a project):
List all NuGet packages and their versions in a .NET project dotnet list package --outdated Search for the malicious package by name dotnet list package | grep -i "Braintree.Net" Check for the companion dependency dotnet list package | grep -i "DependencyInjector.Core" Examine the packages.lock.json for suspicious entries cat packages.lock.json | jq '.targets | keys[]' | grep -i "braintree"
Windows (PowerShell):
List all installed NuGet packages dotnet list package Find Braintree.Net specifically dotnet list package | Select-String "Braintree.Net" Check project file for PackageReference Select-String -Path ".csproj" -Pattern "Braintree.Net" Audit packages.config if using older format findstr /i "Braintree.Net" packages.config
2. Multi-Stage Implant and XOR-Obfuscated C2 Infrastructure
The malicious package operates as a multi-stage .NET implant with sophisticated evasion techniques. Upon assembly load, the code begins intercepting payment activity and capturing information provided during card creation and gateway operations. Rather than breaking the payment process, it blends into it, allowing attackers to obtain data while the application continues functioning normally.
The implant uses XOR obfuscation to conceal its command-and-control (C2) destination. XOR is a simple scrambling method that prevents readable server details from being plainly visible in the package, slowing routine code reviews and making suspicious network connections harder for defenders to identify. The obfuscated C2 server resolves to api.348672-shakepay[.]com, where stolen data is routed.
Most critically, the malware includes production-only gating — it checks whether it is operating in a production environment before activating its key collection routines. This ensures the data theft code remains completely dormant during development and testing, allowing the integration to pass standard quality assurance without raising red flags. Only when deployed to production does the package initiate its three distinct data exfiltration paths.
Network Monitoring Commands:
Linux/macOS:
Monitor outbound connections from .NET processes sudo netstat -tunap | grep dotnet Capture DNS queries to suspicious domains sudo tcpdump -i any -1 port 53 | grep -i "shakepay" Monitor real-time network connections ss -tunap | grep -E "dotnet|443|80" Check for established connections to the C2 domain grep -r "348672-shakepay" /var/log/ 2>/dev/null
Windows (PowerShell):
View active network connections from .NET processes
Get-1etTCPConnection | Where-Object {$_.OwningProcess -in (Get-Process dotnet).Id}
Monitor DNS cache for suspicious entries
ipconfig /displaydns | Select-String "shakepay"
Check firewall logs for outbound connections
Get-WinEvent -LogName "Microsoft-Windows-Windows Firewall With Advanced Security/Firewall" | Where-Object {$_.Message -like "shakepay"}
- Data Exfiltration: PAN, CVV, Merchant Credentials, and Environment Secrets
Once active in production, the malicious package executes three parallel data theft operations:
First, it intercepts payment card details directly from the application’s memory. A hidden logger captures the full Primary Account Number (PAN), Card Verification Value (CVV), and expiration date before the payment request is transmitted to the legitimate Braintree servers. This occurs transparently — the payment process continues as expected, and neither the application nor its users are alerted.
Second, it steals merchant private API keys the moment they are configured in the code. These keys provide attackers with broader access to merchant systems, including the ability to initiate unauthorized transactions, modify payment settings, and access sensitive customer data.
Third, it uses the companion dependency `DependencyInjector.Core` (≥ 1.4.1) — a near-unused package whose primary downstream consumer is this typosquat — to harvest environment variables, configuration files, and access tokens stored by applications. These values can unlock payment services, cloud accounts, databases, and other connected resources, extending the damage well beyond a single compromised application.
All stolen information is bundled and transmitted to the attacker-controlled C2 server. To prevent application crashes that would alert developers, the malware wraps all data-theft operations in empty error-handling blocks — even if the network connection to the attacker’s server fails, the host application continues processing payments as if nothing were wrong.
Credential Audit Commands:
Linux/macOS:
Search for hardcoded API keys in the codebase
grep -rE "BRAINTREE_[A-Za-z0-9_]+" . --include=".cs" --include=".config"
Check environment variables for Braintree credentials
env | grep -i braintree
Examine application configuration files
find . -1ame "appsettings.json" -exec cat {} \; | grep -i braintree
Check for recently modified sensitive files
find / -1ame ".config" -mtime -7 2>/dev/null
Windows (PowerShell):
Search for Braintree credentials in environment variables
Get-ChildItem Env: | Where-Object {$_.Name -like "BRAINTREE"}
Examine appsettings.json files
Get-ChildItem -Recurse -Filter "appsettings.json" | ForEach-Object { Get-Content $_.FullName | Select-String "Braintree" }
Check Windows Registry for stored credentials
Get-ChildItem -Path "HKLM:\SOFTWARE" -Recurse | Where-Object {$_.Name -like "Braintree"}
4. Indicators of Compromise and Threat Hunting
Security researchers have published specific Indicators of Compromise (IOCs) to aid in detection and incident response:
| IOC Type | Value | Description |
|-|-|-|
| SHA-256 | `7a9f19ed663c1d4ee259ba0a10e93e1c9770812ce81f8c945140a452d17cb3c8` | Malicious Braintree.dll |
| SHA-256 | `f181d57c29364aef01e3f72051ec2dc0da918d346e7e4d1377e13408afb8663a` | Malicious Braintree.dll |
| Domain | `api.348672-shakepay[.]com` | C2 exfiltration server |
Threat Hunting Commands:
Linux/macOS:
Search for the malicious DLL by hash
find / -1ame "Braintree.dll" -exec sha256sum {} \; 2>/dev/null | grep -E "7a9f19ed|f181d57c"
Check for unexpected outbound connections to the C2 domain
sudo grep -r "348672-shakepay" /var/log/ 2>/dev/null
Examine assembly metadata for suspicious attributes
find . -1ame ".dll" -exec strings {} \; | grep -i "Braintree.Net" | head -20
Monitor for the companion dependency
dotnet list package | grep -i "DependencyInjector.Core"
Windows (PowerShell):
Search for malicious DLL by hash
Get-ChildItem -Recurse -Filter "Braintree.dll" | ForEach-Object { Get-FileHash $<em>.FullName -Algorithm SHA256 } | Where-Object {$</em>.Hash -in @("7a9f19ed663c1d4ee259ba0a10e93e1c9770812ce81f8c945140a452d17cb3c8","f181d57c29364aef01e3f72051ec2dc0da918d346e7e4d1377e13408afb8663a")}
Check Windows Event Logs for suspicious process creation
Get-WinEvent -LogName "Security" | Where-Object {$<em>.Id -eq 4688 -and $</em>.Message -like "Braintree"}
Examine NuGet package cache
Get-ChildItem "$env:USERPROFILE.nuget\packages\braintree.net" -Recurse
5. Remediation and Mitigation Strategies
Organizations that have installed the affected package must take immediate action:
Immediate Remediation:
- Remove the malicious package from all projects and environments
- Rotate all credentials that were accessible to the compromised application, including Braintree API keys, environment variables, and any tokens stored in configuration files
- Examine dependency records and application logs for unexpected outbound connections
- Treat all payment credentials, tokens, and secrets available to the affected application as potentially exposed
Long-term Mitigation:
- Verify package publishers before approving new dependencies — official Braintree packages are published under the `braintreepayments` profile, not generic “Braintree” claims
- Compare package names carefully — the official package ID is `Braintree` (5.x line), not `Braintree.Net`
3. Review unexpected changes before approving new dependencies
- Implement lock files (
packages.lock.json) and controlled internal repositories to prevent unreviewed packages from reaching production - Monitor outbound traffic from payment applications to reveal suspicious behavior early
- Inspect running applications rather than limiting review to installation time — a dependency that appears harmless at first may activate only when it detects production conditions
NuGet Security Commands:
Enable package lock files for deterministic builds dotnet restore --use-lock-file Verify package source authenticity dotnet nuget verify --all Braintree List all packages with their sources dotnet list package --include-transitive Remove a specific package dotnet remove package Braintree.Net Force package restore from trusted sources only dotnet restore --source https://api.nuget.org/v3/index.json --1o-cache
6. The Broader Supply Chain Threat Landscape
The Braintree.Net typosquat is not an isolated incident. Similar attacks have targeted other financial services, including a malicious `StripeApi.Net` package that impersonated Stripe’s official library to steal API tokens, and `Nethereum` typosquats using homoglyph tricks to steal cryptocurrency wallet keys. The `.NET` ecosystem has also seen campaigns like Tracer.Fody.NLog, which masqueraded as a popular tracing module to exfiltrate cryptocurrency wallets.
These attacks share common patterns: typosquatting on popular package names, fake download statistics to build trust, multi-stage implants that activate only in production, and obfuscated C2 communication to evade detection. The financial sector remains a prime target because payment processing applications handle high-value data and are often integrated into larger production systems with extensive access to sensitive resources.
Developers are the first line of defense. A rushed dependency update or a copy-pasted installation command from an unofficial source can introduce a critical vulnerability into the software supply chain. Security teams must treat every dependency as a potential attack vector and implement rigorous verification processes.
What Undercode Say:
- Typosquatting is a social engineering attack on developers. Attackers exploit human error — a single character difference in a package name can compromise an entire production environment. The Braintree.Net case demonstrates that even experienced developers can fall victim when under time pressure.
-
Production-only activation is the new standard for stealth. By gating malicious behavior to production environments, attackers bypass security testing and quality assurance. This means traditional pre-deployment security scans are no longer sufficient — organizations must monitor runtime behavior in production.
-
Fake download counts are a powerful deception technique. The 32,900x gap between reported downloads (14M) and actual malicious installs (~334) shows how easily attackers can manufacture trust through download inflation. Developers should never rely on download statistics as a security indicator.
-
Companion dependencies enable layered attacks. The use of `DependencyInjector.Core` as a secondary payload carrier demonstrates how attackers can distribute malicious functionality across multiple packages, evading single-package detection and complicating remediation.
-
Credential rotation is the most critical response step. Once a malicious package has been installed, all credentials accessible to the compromised application must be treated as compromised. Delayed rotation gives attackers a window to exploit stolen keys and tokens.
-
The .NET ecosystem is under siege. The frequency of typosquatting attacks targeting NuGet packages is increasing, with attackers focusing on payment gateways and cryptocurrency libraries. Security teams must prioritize dependency management and implement automated threat detection.
Prediction:
-
-1 The Braintree.Net attack represents a maturation of typosquatting techniques that will likely be replicated across other package managers including npm, PyPI, and RubyGems. Attackers will increasingly adopt production-only activation and XOR-obfuscated C2 to evade detection.
-
-1 Financial services organizations will face a wave of similar supply chain attacks targeting payment gateways. The success of this campaign will incentivize threat actors to develop typosquats for other payment processors including Stripe, Adyen, and Square.
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+1 The incident will accelerate adoption of automated dependency scanning tools like Socket, which detected this package within ten minutes. Organizations will increasingly integrate real-time supply chain threat detection into their CI/CD pipelines.
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+1 NuGet and other package managers will be forced to implement stronger package verification mechanisms, potentially including mandatory publisher identity verification and enhanced download statistic transparency to prevent inflation attacks.
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-1 The production-only activation technique will become a standard feature in malicious packages, making traditional sandbox analysis ineffective. Security teams will need to develop new detection methods that monitor runtime behavior in production environments.
-
-1 Small and medium-sized businesses that lack dedicated security teams will be disproportionately affected, as they often rely on trusted package names without implementing rigorous verification processes.
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Reported By: Mayura Kathiresh – Hackers Feeds
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