/etc/sysctl.conf

# Kernel sysctl configuration file for Linux
# Version 1.13 - 2019-3-2
# Day Milovich,,
# credit mentioned below, not by me : )
# nano /etc/sysctl.conf
# edit save exit
# then activate with:
# sysctl -e -p /etc/sysctl.conf
#
# uname -a
# Linux kali 4.18.0-kali2-amd64 #1 SMP Debian 4.18.10-2kali1 (2018-10-09) x86_64 GNU/Linux
# ----------
# Credits:
# http://www.enigma.id.au/linux_tuning.txt
# http://www.securityfocus.com/infocus/1729
# http://fasterdata.es.net/TCP-tuning/linux.html
# http://fedorahosted.org/ktune/browser/sysctl.ktune
# http://www.cymru.com/Documents/ip-stack-tuning.html
# http://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
# http://www.frozentux.net/ipsysctl-tutorial/chunkyhtml/index.html
# http://knol.google.com/k/linux-performance-tuning-and-measurement
# http://www.cyberciti.biz/faq/linux-kernel-tuning-virtual-memory-subsystem/
# http://www.redbooks.ibm.com/abstracts/REDP4285.html
# http://www.speedguide.net/read_articles.php?id=121
# http://lartc.org/howto/lartc.kernel.obscure.html
# http://en.wikipedia.org/wiki/Sysctl

# network security section
# no syn attack, enable syncookies
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_max_syn_backlog = 1024
# no packet forwarding
net.ipv4.ip_forward = 0
net.ipv4.conf.all.forwarding = 0
net.ipv4.conf.default.forwarding = 0
net.ipv6.conf.all.forwarding = 0
net.ipv6.conf.default.forwarding = 0
# no ip source routing
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
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
# ip spoofing protection and source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
# no icmp redir 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
# enable log spoofed packets, source routed packets, redirect packets
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
# decrease the time
net.ipv4.tcp_fin_timeout = 7
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15
# no relay bootp
net.ipv4.conf.all.bootp_relay = 0
# no proxy arp
net.ipv4.conf.all.proxy_arp = 0
# you can not ping me
net.ipv4.icmp_echo_ignore_all = 1
# Enable ignoring broadcasts request
# net.ipv4.icmp_echo_ignore_broadcasts = 1
# Enable bad error message Protection
# net.ipv4.icmp_ignore_bogus_error_responses = 1
# Enable a fix for RFC1337 - time-wait assassination hazards in TCP
# net.ipv4.tcp_rfc1337 = 1
# Do not auto-configure IPv6
# net.ipv6.conf.all.autoconf=0
# net.ipv6.conf.all.accept_ra=0
# net.ipv6.conf.default.autoconf=0
# net.ipv6.conf.default.accept_ra=0
# net.ipv6.conf.eth0.autoconf=0
# net.ipv6.conf.eth0.accept_ra=0
### TUNING NETWORK PERFORMANCE ###
# For high-bandwidth low-latency networks, use 'htcp' congestion control
# Do a 'modprobe tcp_htcp' first
net.ipv4.tcp_congestion_control = htcp
# For servers with tcp-heavy workloads, enable 'fq' queue management scheduler (kernel > 3.12)
net.core.default_qdisc = fq
# Turn on the tcp_window_scaling
net.ipv4.tcp_window_scaling = 1
# Increase the read-buffer space allocatable
net.ipv4.tcp_rmem = 8192 87380 16777216
net.ipv4.udp_rmem_min = 16384
net.core.rmem_default = 262144
net.core.rmem_max = 16777216
# Increase the write-buffer-space allocatable
net.ipv4.tcp_wmem = 8192 65536 16777216
net.ipv4.udp_wmem_min = 16384
net.core.wmem_default = 262144
net.core.wmem_max = 16777216
# Increase number of incoming connections
net.core.somaxconn = 32768
# Increase number of incoming connections backlog
net.core.netdev_max_backlog = 16384
net.core.dev_weight = 64
# Increase the maximum amount of option memory buffers
net.core.optmem_max = 65535
# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks
net.ipv4.tcp_max_tw_buckets = 1440000
# try to reuse time-wait connections, but don't recycle them (recycle can break clients behind NAT)
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_tw_reuse = 1
# Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory
net.ipv4.tcp_max_orphans = 16384
net.ipv4.tcp_orphan_retries = 0
# Limit the maximum memory used to reassemble IP fragments (CVE-2018-5391)
net.ipv4.ipfrag_low_thresh = 196608
net.ipv6.ip6frag_low_thresh = 196608
net.ipv4.ipfrag_high_thresh = 262144
net.ipv6.ip6frag_high_thresh = 262144
# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
# Increase size of RPC datagram queue length
net.unix.max_dgram_qlen = 50
# Don't allow the arp table to become bigger than this
net.ipv4.neigh.default.gc_thresh3 = 2048
# Tell the gc when to become aggressive with arp table cleaning.
# Adjust this based on size of the LAN. 1024 is suitable for most /24 networks
net.ipv4.neigh.default.gc_thresh2 = 1024
# Adjust where the gc will leave arp table alone - set to 32.
net.ipv4.neigh.default.gc_thresh1 = 32
# Adjust to arp table gc to clean-up more often
net.ipv4.neigh.default.gc_interval = 30
# Increase TCP queue length
net.ipv4.neigh.default.proxy_qlen = 96
net.ipv4.neigh.default.unres_qlen = 6
# Enable Explicit Congestion Notification (RFC 3168), disable it if it doesn't work for you
net.ipv4.tcp_ecn = 1
net.ipv4.tcp_reordering = 3
# How many times to retry killing an alive TCP connection
net.ipv4.tcp_retries2 = 15
net.ipv4.tcp_retries1 = 3
# Avoid falling back to slow start after a connection goes idle
# keeps our cwnd large with the keep alive connections (kernel > 3.6)
net.ipv4.tcp_slow_start_after_idle = 0
# Allow the TCP fastopen flag to be used, beware some firewalls do not like TFO! (kernel > 3.7)
net.ipv4.tcp_fastopen = 3
# This will ensure that immediatly subsequent connections use the new values
net.ipv4.route.flush = 1
# net.ipv6.route.flush = 1
### Comments/suggestions/additions are welcome!