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macOS post-exploitation for credential harvesting, DTrace monitoring, TCC bypass, and stealth operations via native tools
Windows userland post-exploitation for credential harvesting, monitoring, AMSI/ETW bypass, and stealth operations
Kubernetes post-exploitation for container escape, secret extraction, RBAC abuse, and cluster persistence
Based on SOC occupation classification
Showing SKILL.md
| name | cis-gcp-cos-3.2.7 |
| description | Ensure Reverse Path Filtering is enabled |
| category | cis-gcp-cos |
| version | 1.2.0 |
| author | cyberstrike-official |
| tags | ["cis","gcp","container-optimized-os","network","sysctl","routing"] |
| cis_id | 3.2.7 |
| cis_benchmark | CIS Google Container-Optimized OS Benchmark v1.2.0 |
| tech_stack | ["gcp","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
Setting net.ipv4.conf.all.rp_filter and net.ipv4.conf.default.rp_filter to 1 forces the Linux kernel to utilize reverse path filtering on a received packet to determine if the packet was valid. Essentially, with reverse path filtering, if the return packet does not go out the same interface that the corresponding source packet came from, the packet is dropped (and logged if log_martians is set).
Setting these flags is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing.
Run the following commands and verify output matches:
# sysctl net.ipv4.conf.all.rp_filter
net.ipv4.conf.all.rp_filter = 1
# sysctl net.ipv4.conf.default.rp_filter
net.ipv4.conf.default.rp_filter = 1
# grep "net\.ipv4\.conf\.all\.rp_filter" /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.conf.all.rp_filter = 1
# grep "net\.ipv4\.conf\.default\.rp_filter" /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.conf.default.rp_filter = 1
All sysctl commands should return a value of 1 and grep commands should confirm the settings are persisted in the sysctl configuration files.
Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
Run the following commands to set the active kernel parameters:
# sysctl -w net.ipv4.conf.all.rp_filter=1
# sysctl -w net.ipv4.conf.default.rp_filter=1
# sysctl -w net.ipv4.route.flush=1
/etc is stateless on Container-Optimized OS. Therefore, /etc cannot be used to make these changes persistent across reboots. The steps mentioned above needs to be performed after every boot.
| Controls Version |
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| Control |
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| IG 1 |
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| IG 2 |
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| IG 3 |
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| v8 | 12.2 Establish and Maintain a Secure Network Architecture - Establish and maintain a secure network architecture. A secure network architecture must address segmentation, least privilege, and availability, at a minimum. | X | X | |
| v7 | 5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software. | X | X | X |