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    NixSec

    Sysctl Tweaks

    Edit /etc/sysctl.conf

    # vi /etc/sysctl.conf
    

    Add the following items at the bottom.

    # Controls the System Request debugging functionality of the kernel
    kernel.sysrq = 0
    # Controls whether core dumps will append the PID to the core filename, usef$
    kernel.core_uses_pid = 1
    
    # Controls IP packet forwarding
    net.ipv4.ip_forward = 1
    # Controls source route verification
    net.ipv4.conf.default.rp_filter = 1
    # Do not accept source routing
    net.ipv4.conf.default.accept_source_route = 0
    
    net.ipv4.conf.all.src_valid_mark=1
    # Controls of how network trust neighbours (not!)
    net.ipv4.conf.all.secure_redirects = 0
    net.ipv4.conf.all.accept_redirects = 0
    net.ipv4.conf.all.accept_source_route = 0
    net.ipv4.conf.all.send_redirects = 0
    
    # Controls the use of TCP syncookies
    net.ipv4.tcp_syncookies = 1
    # Controls of syn backlog
    net.ipv4.tcp_max_syn_backlog = 4096
    
    # Default ipv4 settings for usage on load balanced hosts.
    net.ipv4.conf.lo.arp_ignore = 1
    net.ipv4.conf.lo.arp_announce = 2
    net.ipv4.conf.all.arp_ignore = 1
    net.ipv4.conf.all.arp_announce = 2
    net.ipv4.tcp_mem = 786432 1048576 1572864
    net.ipv4.tcp_tw_recycle = 1
    
    # Default ipv4 connection tracking tweaks
    net.netfilter.nf_conntrack_tcp_timeout_syn_recv = 30
    net.netfilter.nf_conntrack_tcp_timeout_time_wait = 60
    net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 30
    net.netfilter.nf_conntrack_tcp_timeout_close_wait = 30
    net.netfilter.nf_conntrack_tcp_timeout_established = 600
    net.netfilter.nf_conntrack_max = 1048576
    
    # Disable ipv6
    net.ipv6.conf.all.disable_ipv6 = 1
    net.ipv6.conf.default.disable_ipv6 = 1
    net.ipv6.conf.lo.disable_ipv6 = 1
    
    # Disable ipv6 router advertisement addresses
    net.ipv6.conf.all.accept_ra = 0
    net.ipv6.conf.ens192.accept_ra = 0
    net.ipv6.conf.default.accept_ra = 0
    
    # Disable ipv6 autoconfiguration
    net.ipv6.conf.all.autoconf = 0
    net.ipv6.conf.ens192.autoconf = 0
    net.ipv6.conf.default.autoconf = 0
    
    kernel.shmmax = 2147483648
    kernel.shmmni = 4096
    kernel.sem = 250 32000 100 128
    
    # TCP Performance tweaks
    net.ipv4.tcp_window_scaling = 1
    net.ipv4.tcp_timestamps = 1
    net.ipv4.tcp_syncookies = 1
    net.core.rmem_max = 16777216
    net.core.wmem_max = 16777216
    net.core.wmem_max = 4194304
    
    
    ### IMPROVE SYSTEM MEMORY MANAGEMENT ###
    
    # Increase size of file handles and inode cache
    fs.file-max = 2097152
    
    # Do less swapping
    vm.swappiness = 10
    vm.dirty_ratio = 60
    vm.dirty_background_ratio = 2
    
    ### GENERAL NETWORK SECURITY OPTIONS ###
    
    # Number of times SYNACKs for passive TCP connection.
    net.ipv4.tcp_synack_retries = 2
    
    # Allowed local port range
    net.ipv4.ip_local_port_range = 2000 65535
    
    # Protect Against TCP Time-Wait
    net.ipv4.tcp_rfc1337 = 1
    
    # Decrease the time default value for tcp_fin_timeout connection
    net.ipv4.tcp_fin_timeout = 15
    
    # Decrease the time default value for connections to keep alive
    net.ipv4.tcp_keepalive_time = 300
    net.ipv4.tcp_keepalive_probes = 5
    net.ipv4.tcp_keepalive_intvl = 15
    
    ### TUNING NETWORK PERFORMANCE ###
    
    # Default Socket Receive Buffer
    net.core.rmem_default = 31457280
    
    # Maximum Socket Receive Buffer
    net.core.rmem_max = 12582912
    
    # Default Socket Send Buffer
    net.core.wmem_default = 31457280
    
    # Maximum Socket Send Buffer
    net.core.wmem_max = 12582912
    
    # Increase number of incoming connections
    net.core.somaxconn = 4096
    
    # Increase number of incoming connections backlog
    net.core.netdev_max_backlog = 65536
    
    # Increase the maximum amount of option memory buffers
    net.core.optmem_max = 25165824
    
    # Increase the maximum total buffer-space allocatable
    # This is measured in units of pages (4096 bytes)
    net.ipv4.tcp_mem = 65536 131072 262144
    net.ipv4.udp_mem = 65536 131072 262144
    
    # Increase the read-buffer space allocatable
    net.ipv4.tcp_rmem = 8192 87380 16777216
    net.ipv4.udp_rmem_min = 16384
    
    # Increase the write-buffer-space allocatable
    net.ipv4.tcp_wmem = 8192 65536 16777216
    net.ipv4.udp_wmem_min = 16384
    
    # Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks
    net.ipv4.tcp_max_tw_buckets = 1440000
    net.ipv4.tcp_tw_recycle = 1
    net.ipv4.tcp_tw_reuse = 1
    net.ipv4.tcp_low_latency = 1