Create Internet-to-Data-Center DoS Protection Policy Rules

Protect your data center web servers and the firewall from DoS attacks to prevent attackers from taking down your data center network.
One method attackers use to disrupt a network is a Denial-of-Service (DoS) attack intended to overwhelm targeted systems that are connected to the internet, take them down, and make them unavailable to all of your legitimate users and services. Data center web servers are an attractive target because taking them down prevents most legitimate access to the data center.
Protect the data center web server tier by applying a classified DoS Protection Policy to internet traffic destined for those servers. A classified DoS Protection policy applies a classified DoS Protection Profile that controls the number of incoming connections to the traffic defined in the policy.
In addition, configure packet buffer protection for each zone to protect the firewall from single-session DOS attacks that can overwhelm the firewall’s packet buffer and cause legitimate traffic to drop, especially on firewalls that protect critical services.
  1. Create a classified DoS Protection Profile that protects data center web servers from DoS attacks by limiting the number of connections-per-second to prevent a SYN flood attack.
    This DoS Protection profile limits the number of connections-per-second (CPS) for the traffic defined in the DoS Protection Policy rules to which you attach the profile, to prevent a DoS attack from taking down your web servers. The profile sets progressive CPS thresholds to alert you, to activate Random Early Drop (RED) packet drop, and to block new connections, as well as a duration during which new connections remain blocked. The CPS thresholds you configure to protect your data center web servers depends on the capacity of your web servers.
    To create this profile:
    • At
      Security Profiles
      DoS Protection
      a classified DoS Protection Profile.
    • Name
      the profile, select
      as the profile
      , set the CPS values to alert (
      Alarm Rate
      ), activate RED (
      Activate Rate
      ), begin blocking new sessions (
      Max Rate
      ), and set the amount of time in seconds to block new sessions (
      Block Duration
      ) when the CPS rate reaches the
      Max Rate
    If you don’t use protocols such as UDP or other IP protocols, restrict them using a combination of Security policy rules to allow applications and Zone Protection Profiles to block unused protocols by setting flood protection CPS to zero packets for protocols you want to block.
  2. Create a classified DoS Protection policy rule to define the servers you want to protect from a DoS attack and attach the DoS Protection profile to it.
    This rule prevents a SYN flood attack from taking down your data center web server tier. This example applies the classified DoS Protection profile to external traffic allowed to connect to the web server tier.
    To create this rule:
    • To apply DoS protection to traffic destined for the web server tier, the DoS Protection policy must apply to the same traffic as the Security Policy rule that allows the traffic. In this example, this DoS rule protects the traffic we allowed in Create Internet-to-Data-Center Application Allow Rules.
    • On the Option/Protection tab, specify the web services (
      ), set the Action to
      to apply the DoS Protection profile’s SYN flood thresholds to the traffic, set the Log Forwarding method (assuming that you have configured log forwarding), and select the classified DoS Protection profile we configured for the traffic in the preceding step (
      Internet to DC
    To protect against SYN flood attacks from internal sources, create a separate DoS Protection policy rule that specifies your internal zones as the source zone instead of
    . Creating separate rules for external and internal attack sources provides separate reporting that makes investigating attack attempts easier.

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