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security/hardening/linux-hardening/assets/sysctl-hardening.conf

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+# Linux Kernel Security Hardening
+# Place in /etc/sysctl.d/99-security.conf
+# Apply with: sysctl -p /etc/sysctl.d/99-security.conf
+
+#------------------------------------------------------------------------------
+# NETWORK SECURITY
+#------------------------------------------------------------------------------
+
+# Disable IP forwarding (unless router)
+net.ipv4.ip_forward = 0
+net.ipv6.conf.all.forwarding = 0
+
+# Disable packet redirect sending
+net.ipv4.conf.all.send_redirects = 0
+net.ipv4.conf.default.send_redirects = 0
+
+# Disable ICMP redirect acceptance
+net.ipv4.conf.all.accept_redirects = 0
+net.ipv4.conf.default.accept_redirects = 0
+net.ipv4.conf.all.secure_redirects = 0
+net.ipv4.conf.default.secure_redirects = 0
+net.ipv6.conf.all.accept_redirects = 0
+net.ipv6.conf.default.accept_redirects = 0
+
+# Disable source routing
+net.ipv4.conf.all.accept_source_route = 0
+net.ipv4.conf.default.accept_source_route = 0
+net.ipv6.conf.all.accept_source_route = 0
+net.ipv6.conf.default.accept_source_route = 0
+
+# Log suspicious packets
+net.ipv4.conf.all.log_martians = 1
+net.ipv4.conf.default.log_martians = 1
+
+# Ignore ICMP broadcast requests
+net.ipv4.icmp_echo_ignore_broadcasts = 1
+
+# Ignore bogus ICMP error responses
+net.ipv4.icmp_ignore_bogus_error_responses = 1
+
+# Enable reverse path filtering (spoofing protection)
+net.ipv4.conf.all.rp_filter = 1
+net.ipv4.conf.default.rp_filter = 1
+
+# Enable TCP SYN cookies (SYN flood protection)
+net.ipv4.tcp_syncookies = 1
+
+# Disable IPv6 router advertisements
+net.ipv6.conf.all.accept_ra = 0
+net.ipv6.conf.default.accept_ra = 0
+
+# Disable IPv6 if not needed
+# net.ipv6.conf.all.disable_ipv6 = 1
+# net.ipv6.conf.default.disable_ipv6 = 1
+
+#------------------------------------------------------------------------------
+# KERNEL SECURITY
+#------------------------------------------------------------------------------
+
+# Enable ASLR
+kernel.randomize_va_space = 2
+
+# Restrict access to kernel pointers
+kernel.kptr_restrict = 2
+
+# Restrict dmesg access
+kernel.dmesg_restrict = 1
+
+# Restrict ptrace scope
+kernel.yama.ptrace_scope = 1
+
+# Disable magic SysRq key
+kernel.sysrq = 0
+
+# Restrict unprivileged user namespaces
+# kernel.unprivileged_userns_clone = 0
+
+# Restrict loading TTY line disciplines
+dev.tty.ldisc_autoload = 0
+
+# Restrict userfaultfd to privileged users
+vm.unprivileged_userfaultfd = 0
+
+# Restrict BPF
+kernel.unprivileged_bpf_disabled = 1
+net.core.bpf_jit_harden = 2
+
+# Restrict perf events
+kernel.perf_event_paranoid = 3
+
+#------------------------------------------------------------------------------
+# FILE SYSTEM SECURITY
+#------------------------------------------------------------------------------
+
+# Restrict core dumps
+fs.suid_dumpable = 0
+
+# Restrict hardlinks and symlinks
+fs.protected_hardlinks = 1
+fs.protected_symlinks = 1
+
+# Protect FIFOs and regular files
+fs.protected_fifos = 2
+fs.protected_regular = 2