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Firewall Best Practices

10 Firewall best practices for network Security Admins

You shall not pass!
Keep your network safe from hackers.

Keep your network safe from hackers

Keep your network safe from hackers

Your firewall is the first line of defense against security threats, but as you may already know, simply adding firewall devices and security modules to your network doesn’t ensure your network is more secure. You need to regularly watch and analyze your firewall’s sys logs and configurations, and optimize its performance to protect your network.
The heart of any firewall’s performance is its rules and policies. If not managed properly, these can leave your
network vulnerable to attacks.

Gartner predicts that 99 percent of exploited vulnerabilities will continue to be ones known by security and IT professionals for at least one year. Gartner concludes that the best and cheapest way to mitigate cyberattacks
caused by known vulnerabilities is by removing them altogether with regular patching.

For many security admins, maintaining optimal rule performance is a daunting task. Businesses are demanding that networks perform faster, leaving security admins balancing on the thin line separating speed and security. With these challenges in mind, here are some firewall best practices that can help security admins handle the conundrum of speed vs. security.

Firewall best practices

1. Document firewall rules and add comments to explain special rules.

It’s critical for everyone in an IT team to have visibility over all the rules that have been written. Along with the list of rules, it’s important to record: It’s better to be safe than sorry; it’s good practice to start off writing firewall rules with a “deny all” rule. This helps protect your network from manual errors. After testing and deploying the rules, it’s a good idea to special rules.

  • The purpose of a rule.
  • The name of the security admin who wrote the rule, along with date of creation.
  • The users and services affected by the rule.
  • The devices and interfaces affected by the rule.
  • Rule expiration date.

You can record this information as comments when creating a new rule or modifying an existing rule. The first thing you should do, if you haven’t already, is review all the existing rules, and document the above information wherever possible. Though this might be a time-consuming task, you’ll only have to do it once, and it’ll end up saving you a lot of time when auditing and adding new rules in the long run.

2. Reduce over-permissive rules and include “deny all or deny rest” wherever necessary.

It’s better to be safe than sorry; it’s good practice to start off writing firewall rules with a “deny all” rule. This helps protect your network from manual errors. After testing and deploying the rules, it’s a good idea to include a “deny rest” at the bottom. This ensures that your firewall allows only the required traffic and blocks the rest. You’ll also want to avoid using over-permissive rules like “allow any” as this can put your network at risk.

Permissive rules give users more freedom, which can translate into granting users access to more resources than they need to perform business-related functions. This leads to two types of problems:

  • Under or overutilized network bandwidth.
  • Increased exposure to potentially malicious sites.

Restrict over-permissive rules, and avoid these issues altogether.

3. Review firewall rules regularly. Organize firewall rules to maximize speed and performance.

As years go by and new policies are defined by different security admins, the number of rules tends to pile up. When new rules are defined without analyzing the old ones, these rules become redundant and can contradict each other, causing anomalies that negatively affect your firewall’s performance. Cleaning up unused rules on a regular basis
helps avoid clogging up your firewall’s processor, so it’s important to periodically audit rules as well as remove duplicate rules, anomalies, and unwanted policies.

Placing the most used rules on top and moving the lesser-used rules to the bottom helps improve the processing capacity of your firewall. This is an activity that should be performed periodically, as different types of rules are used at different times.

4. Check the health of your rules with a penetration test.

A penetration test is a simulated cyber attack against your computer system that checks for exploitable vulnerabilities. Just like how cars undergo crash tests to detect holes in the safety design, periodic penetration tests on your firewall will help you identify areas in your network’s security that are vulnerable.

5. Automate security audits.

A security audit is a manual or systematic measurable technical assessment of the firewall. Given that it consists of a combination of manual and automated tasks, auditing and recording the results of these tasks on a regular basis is essential. You need a tool that can both automate tasks and record results from manual tasks. This will help track
how configuration changes impact the firewall.

6. Implement an end-to-end change management tool.

The key to efficient policy management is an end-to-end change management tool that can track and record requests from start to finish. A typical change procedure might involve the following steps:

End-to-end configuration change monitoring

User request = > Request approval = >  Testing = > Deployment = > Validation

  • A user raises a request for a particular change.
  • The request is approved by the firewall or network security team, and all the details on who approves the request are recorded for future reference.
  • After approval, the configuration is tested to confirm whether changes in the firewall will have the desired effect without causing any threat to the existing setup.
  • Once the changes are tested, the new rule is deployed into production.
  • A validation process is performed to ensure that the new firewall settings are operating as intended.
  • All changes, reasons for changes, time stamps, and personnel involved are recorded.

7. Lay out an extensive, real-time alert management plan.

A real-time alert management system is critical for efficient firewall management. You need to:

  • Monitor the availability of the firewall in real time. If a firewall goes down, an alternate firewall needs to immediately go up so all traffic can be routed through this firewall for the time being.
  • Trigger alarms when the system encounters an attack so that the issue can be quickly rectified.
  • Set alert notifications for all the changes that are made. This will help security admins keep a close eye on every change as it happens.

8. Retain logs as per regulations.

You need to retain logs for a stipulated amount of time depending on which regulations you need to comply with. Below are some of the major compliance standards along with the retention period required for each regulation.

Regulation

Retention requirement

PCI DSS

1 year

ISO 27001

3 years

NIST

3 years

NERC CIP

3 years

HIPAA

7 years

FISMA

3 years

GLBA

6 years

SOX

7 years

Different countries have different regulations on how long logs need to be stored for legal and auditing purposes. You should check with your legal team on which regulations your business needs to comply with. Regular internal audits, combined with compliance checks for different security standards, are important aspects of maintaining a healthy network. Every company will follow different compliance standards based on the industry that business is in. You can automate compliance checks and audits to run on a regular basis to ensure you’re meeting industry standards.

9. Periodically check for security compliance.

Regular internal audits, combined with compliance checks for different security standards, are important aspects of maintaining a healthy network. Every company will follow different compliance standards based on the industry that business is in. You can automate compliance checks and audits to run on a regular basis to ensure you’re meeting
industry standards.

10. Upgrade your firewall software and firmware.

No network or firewall is perfect, and hackers are working around the clock to find any loopholes they can. Regular software and firmware updates to your firewall help eliminate known vulnerabilities in your system. Not even the best set of firewall rules can stop an attack if a known vulnerability hasn’t been patched.

 

Firewall Analyzer can help in adhering to these firewall best practices.

1. Rule Management:

Policy Overview: Manually documenting all firewall rules and reviewing them on a regular basis is an arduous and time-consuming task. To solve this issue, you can use Firewall Analyzer to fetch the entire set of rules written for your firewall. To simplify review, you can also filter rules on the following criteria:

• Allowed and denied rules.
• Inbound and outbound rules.
• Inactive rules.
• Rules with logging disabled.
• Over-permissive, any-to-any rules.

Policy Optimization: Firewall Analyzer’s Policy Optimization feature identifies shadow rules, redundancy,  generalization, correlation, and grouping anomalies. These anomalies negatively impact firewall performance, and removing them will help you optimize rule efficiency.

Rule Reorder: Firewall Analyzer provides suggestions on rule position by correlating the number of rule hits with rule complexity and anomalies. It can estimate the performance improvement for a suggested change.

Rule Cleanup: Firewall Analyzer provides a detailed list of all unused firewall rules, objects, and interfaces. The Rule Cleanup feature gives you a high-level overview of which rules, objects, and interfaces can be removed or deactivated. As you can see, Firewall Analyzer doesn’t just provide visibility into firewall rules; its in-depth Rule Optimization and Rule Reorder reports help in removing rule anomalies and inefficiencies in rule performance.
Together these reports help in:

• Documenting firewall rules.
• Reviewing firewall rules.
• Optimizing firewall performance.
• Organizing firewall rules to maximize speed.

2. Configuration Change Management: Firewall Analyzer fetches configuration changes from firewall devices and generates the following Change Management report.

This report helps you find who made what changes, when, and why. Firewall Analyzer also sends real-time alerts to your phone when changes happen. This report ensures that all configurations and subsequent changes made in your firewall are captured periodically and stored in a database.

With a combination of ManageEngine’s ServiceDesk Plus for ticketing and Firewall Analyzer for monitoring configuration changes, security admins gain end-to-end change monitoring. This type of end-to-end change monitoring system is critical for avoiding security events caused by human error.

3. Compliance Reports: Firewall Analyzer generates out-of-the-box compliance reports for the following industry standards:

  • Payment Card Industry Data Security Standard (PCI DSS)
  • ISO 27001:2013
  • Firewall best practices
  • NIST Special Publication 800-53
  • NERC’s Critical Infrastructure Protection (CIP) Standards
  • SANS Institutes’ Firewall Checklist

With these reports, you can track your firewall devices’ compliance status in terms of configurations.

4. Configuration Security Audits: Firewall Analyzer can perform security audits on the configuration setup of your firewall and provide detailed reports on any security loopholes. Firewall Analyzer also provides the severity of loopholes, ease of attack due to these loopholes, and a recommendation on how to fix reported issues.

5. Alarm Management: With Firewall Analyzer, you can set alarm notifications for both security and traffic incidents. Firewall Analyzer monitors syslogs, and sends out a notification whenever an alarm threshold trigger is passed. Alert notifications can either be sent via email or SMS. Firewall Analyzer’s alarms help you identify security and traffic events as soon as they occur.

6. Log Retention: With Firewall Analyzer, you can either retain logs in the database or the archive. You can also set a time period for log retention to save disk space and improve performance; after all, disk space requirements can exceed 10TB if log data needs to be retained for a full year.

Continuously monitoring and reviewing your firewall rules, configuration and logs play an important role in securing your network.

With the ManageEngine’s Firewall Analyzer, you can

  • Document and review firewall rules.
  • Organize firewall rules to maximize speed.
  • Monitor all configuration changes made to the firewall.
  • Perform forensic analysis on firewall logs.
  • Set alarm notifications for traffic and security anomalies.
  • Generate compliance reports and perform security audits.

To maintain your firewall rules and adhere to the best practices, Please contact us on

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Firewall Checklist

Firewall Hardening Checklist

Firewall Hardening Checklist

Firewall Hardening Checklist

This checklist should be used to audit a firewall. This checklist does not provide vendor specific security considerations but rather attempts to provide a generic listing of security considerations to be used when auditing a firewall.Only technical aspects of security are addressed in this checklist. Manual elements like physical protection for the firewall server is not considered.

Prior to using this checklist the following elements should be considered:

  • Operating system: This checklist only defines the security items relating the firewall software and not to any security elements of the operating system.
  • Port restrictions: A listing of ports to be restricted are highlighted in this checklist.However, prior to recommending that the ports be restricted, the auditor should ensure that the service associated with that port is not used by the business e.g.remote access via telnet. Where such situations exist this checklist attempts to provide alternate security options if the service is needed e.g. use SSH instead of Telnet.
  • Modems within the internal network: Modems within the internal network are the biggest threat to subvert a firewall and thus the auditor should ensure that there of 6are no modems within the internal network. It is senseless performing an audition the firewall when an even bigger threat exists via the modem. The auditor should perform war dialing to identify any modems within the internal network with tools like phone sweeper.
  • Application level firewalls: The inherent nature of application level firewalls require that the operating system be as secure as possible due to the close binding of these two components. Thus, the auditor should ensure that the security on the operating system is secure before evaluating the security offered by the application level firewall.
  • De fence in depth: It must be recognized that the firewall implementation is a notan end to itself to provide security. Thus, it is vital that the auditor evaluate the security of the other components like IDS, operating systems, web applications,IIS/Apache, routers and databases. Some organizations have opted for firewall network appliances, which are firewalls loaded onto operating systems which have their security already pre configured. In such instances, the auditor need only review the security of the firewall configuration instead of the operating system as well.
  • Rulesets: This checklist provides a listing of best practice rule sets to be applied.However, the organizational requirements may not need all of the rule sets. Fore.g. where an organization has a need to allow access via the internet to critical servers, the rule sets wound not include a deny rule to that internal IP address forthe critical server. Instead it may provide for allow access to HTTP 80 to the critical IP and deny all other traffic to the critical IP. It must be noted that some elements of the recommended rule sets have to be applied irrespective of business requirements e.g. blocking private addresses (RFC1918), illegal addresses, standard unroutables, reserved addresses, etc.
  • Laptop users: Most organizations use mobile laptops for telecommuting and on the road sales, etc. This provides a further vulnerability even if the organization operates a VPN. The hacker could easily gain access to the laptop when it is connected to the internet and download tools to the laptop that can become a problem when the laptop is again connected to the corporate network. In a VPN situation, the hacker with access to the remote station once the tunnel is connected, can access the corporate network. In such a circumstance, it is important for the auditor to determine if laptop usage occurs and to evaluate whether personal firewalls are installed on these laptops prior to usage. This checklist provides a generic set of considerations for personal firewalls, but it does not provide any product specific security recommendations.

Checklist

Checklist

Checklist

No.Security Elements
1.Review the rulesets to ensure that they follow the order as follows:
•   anti-spoofing filters (blocked private addresses, internal addresses
appearing from the outside)
•   User permit rules (e.g. allow HTTP to public webserver)
•   Management permit rules (e.g. SNMP traps to network
management server)
•   Noise drops (e.g. discard OSPF and HSRP chatter)
•   Deny and Alert (alert systems administrator about traffic that is
suspicious)
•   Deny and log (log remaining traffic for analysis)
Firewalls operate on a first match basis, thus the above structure is important
to ensure that suspicious traffic is kept out instead of inadvertently allowing
them in by not following the proper order.

 

2. Application based firewall
Ensure that the administrators monitor any attempts to violate the security policy using the audit logs generated by the application level firewall. Alternatively some application level firewalls provide the functionality to log to intrusion detection systems. In such a circumstance ensure that the correct host, which is hosting the IDS, is defined in the application level firewall. Ensure that there is a process to update the application level firewall’s vulnerabilities checked to the most current vulnerabilities.Ensure that there is a process to update the software with the latest attack signatures.In the event of the signatures being downloaded from the vendors’ site, ensure that it is a trusted site.

In the event of the signature being e-mailed to the systems administrator, ensure that digital signatures are used to verify the vendor and that the information transmitted has not been modified en-route.

The following commands should be blocked for SMTP at the application level firewall:

  • EXPN (expand)
  • VRFY (verify)
  • DEBUG
  • WIZARD

The following command should be blocked for FTP:

  • PUT

Review the denied URL’s and ensure that they are appropriate for e.g. any URL’s to hacker sites should be blocked. In some instances organisations may want to block access to x-rated sites or other harmful sites. As such they would subscribe to sites, which maintain listings of such harmful sites. Ensure that the URL’s to deny are updated as released by the sites that warn of harmful sites.

Ensure that only authorised users are authenticated by the application level firewall.

3. Stateful inspection

Review the state tables to ensure that appropriate rules are set up in terms of source and destination IP’s, source and destination ports and timeouts. Ensure that the timeouts are appropriate so as not to give the hacker too much time to launch a successful attack.

For URL’s

  • If a URL filtering server is used, ensure that it is appropriately defined in the firewall software. If the filtering server is external to the organisation ensure that it is a trusted source.
  • If the URL is from a file, ensure that there is adequate protection for this file to ensure no unauthorised modifications.

Ensure that specific traffic containing scripts; ActiveX and java are striped prior to being allowed into the internal network.

If filtering on MAC addresses is allowed, review the filters to ensure that it is restricted to the appropriate MAC’s as defined in the security policy.

  1. Logging
    Ensure that logging is enabled and that the logs are reviewed to identify any potential patterns that could indicate an attack.
  2. Patches and updates
    Ensure that the latest patches and updates relating to your firewall product is tested and installed.
    If patches and updates are automatically downloaded from the vendors’ websites, ensure that the update is received from a trusted site.
In the event that patches and updates are e-mailed to the systems
administrator ensure that digital signatures are used to verify the vendor and
ensure that the information has not been modified en-route.
6.Location – DMZ
Ensure that there are two firewalls – one to connect the web server to the
internet and the other to connect the web server to the internal network.
In the event of two firewalls ensure that it is of different types and that dual
NIC’s are used. This would increase security since a hacker would need to
have knowledge of the strengths, weaknesses and bugs of both firewalls.
The rulesets for both firewalls would vary based on their location e.g. between
web server and the internet and between web server and the internal network.
7.Vulnerability assessments/ Testing
Ascertain if there is a procedure to test for open ports using nmap and whether
unnecessary ports are closed.
Ensure that there is a procedure to test the rulesets when established or
changed so as not to create a denial of service on the organisation or allow
any weaknesses to continue undetected.
8.Compliance with security policy
Ensure that the ruleset complies with the organisation security policy.
9.Ensure that the following spoofed, private (RFC 1918) and illegal addresses
are blocked:
Standard unroutables
•255.255.255.255
•127.0.0.0
Private (RFC 1918) addresses
•10.0.0.0 – 10.255.255.255
•172.16.0.0 – 172.31.255.255
•192.168.0.0– 192.168.255.255
Reserved addresses
•240.0.0.0
Illegal addresses
•0.0.0.0
UDP echo
ICMP broadcast (RFC 2644)
Ensure that traffic from the above addresses is not transmitted by the
interface.
10.Ensure that loose source routing and strict source routing (lsrsr & ssrr) are
blocked and logged by the firewall.
11.Port restrictions
The following ports should blocked:
ServicePort TypePort Number
DNS Zone TransfersTCP53
TFTP DaemonUDP69
LinkTCP87
SUN RPCTCP & UDP111
BSD UNIXTCP512 – 514
LPDTCP515
UUCPDTCP540
Open WindowsTCP & UDP2000
NFSTCP & UDP2049
X WindowsTCP & UDP6000 – 6255
Small servicesTCP & UDP20 and below

 

Small servicesTCP & UDP20 and below
FTPTCP21
SSHTCP22
TelnetTCP23
SMTP (except externalTCP25
mail relays)
NTPTCP & UDP37
FingerTCP79
HTTP (except to externalTCP80
web servers)
POPTCP109&110
NNTPTCP119
NTPTCP123
NetBIOS in Windows NTTCP &UDP135
NetBIOS in Windows NTUDP137& 138
NetBIOSTCP139
IMAPTCP143
SNMPTCP161&162
SNMPUDP161&162
BGPTCP179
LDAPTCP &UDP389
SSL (except to externalTCP443
web servers)
NetBIOS in Win2kTCP &UDP445
SyslogUDP514
SOCKSTCP1080
Cisco AUX portTCP2001
Cisco AUX port (stream)TCP4001
Lockd (Linux DoSTCP &UDP4045
Vulnerability)
Cisco AUX port (binary)TCP6001
Common high orderTCP8000, 8080, 8888
HTTP ports
  1. Remote access
    If remote access is to be used, ensure that the SSH protocol (port 22) is used instead of Telnet.
  2. File Transfers
    If FTP is a requirement, ensure that the server, which supports FTP, is placed in a different subnet than the internal protected network.
  3. Mail Traffic
    Ascertain which protocol is used for mail and ensure that there is a rule to block incoming mail traffic except to internal mail.
  4. ICMP (ICMP 8, 11, 3)
    Ensure that there is a rule blocking ICMP echo requests and replies.
    Ensure that there is a rule blocking outgoing time exceeded and unreachable messages.
  5. IP Readdressing/IP Masquerading
    Ensure that the firewall rules have the readdressing option enabled such that internal IP addresses are not displayed to the external untrusted networks.
  6. Zone Transfers
    If the firewall is stateful, ensure packet filtering for UDP/TCP 53. IP packets for UDP 53 from the Internet are limited to authorised replies from the internal network. If the packet were not replying to a request from the internal DNS server, the firewall would deny it. The firewall is also denying IP packets for TCP 53 on the internal DNS server, besides those from authorised external secondary DNS servers, to prevent unauthorised zone transfers.
  7. Egress Filtering
    Ensure that there is a rule specifying that only traffic originating from IP’s within the internal network be allowed. Traffic with IP’s other than from the Internal network are to be dropped.
    Ensure that any traffic originating from IP’s other than from the internal network are logged.
  8. Critical servers
    Ensure that there is a deny rule for traffic destined to critical internal addresses from external sources. This rule is based on the organisational requirements, since some organisations may allow traffic via a web application to be routed via a DMZ.
  9. Personal firewalls
    Ensure that laptop users are given appropriate training regarding the threats, types of elements blocked by the firewall and guidelines for operation of the personal firewall. This element is essential, since often times personal firewalls rely on user prompt to respond to attacks e.g. whether to accept/deny a request from a specific address.
    Review the security settings of the personal firewall to ensure that it restricts access to specific ports, protects against known attacks, and that there is adequate logging and user alerts in the event of an intrusion.
    Ensure that there is a procedure to update the software for any new attacks that become known.
    Alternatively most tools provide the option of transferring automatic updates via the internet. In such instances ensure that updates are received from trusted sites.
  10. Distributed firewalls Ensure that the security policy is consistently distributed to all hosts especially when there are changes to the policy. Ensure that there are adequate controls to ensure the integrity of the policy during transfer, e.g. IPSec to encrypt the policy when in transfer. Ensure that there are adequate controls to authenticate the appropriate host. Again IPSec can be used for authentication with cryptographic certificates.
  11. Stealth Firewalls Ensure that default users and passwords are reset. Ensure that the firewall is appropriately configured to know which hosts are on which interface. Review the firewall access control lists to ensure that the appropriate traffic is routed to the appropriate segments. A stealth firewall does not have a presence on the network it is protecting and it makes it more difficult for the hacker to determine which firewall product is being used and their versions and to ascertain the topology of the network.
  12. Ensure that ACK bit monitoring is established to ensure that a remote system cannot initiate a TCP connection, but can only respond to packets sent to it.
  13. Continued availability of Firewalls: Ensure that there is a hot standby for the primary firewall.

 

Cyber Security Predictions: 2019 and Beyond

As you think about how to deploy in advance of a new year of cyber threats, here are the trends and activities most likely to affect your organization

In anticipating the major cyber security and privacy trends for the coming year, you can find plenty of clues in the events of the past 12 months. Among the now familiar forms of attack, cyber hacks of major corporate systems and websites continued in 2018 and will inevitably be part of the 2019 cyber security scene. Many well-known organizations around the world suffered significant breaches this year. The single largest potential data leak, affecting marketing and data aggregation firm Exactis, involved the exposure of a database that contained nearly 340 million personal information records.

Beyond all-too-common corporate attacks, 2018 saw accelerated threat activity across a diverse range of targets and victims. In the social networking realm, Facebook estimated that hackers stole user information from nearly 30 million people. A growing assortment of nation-states used cyber probes and attacks to access everything from corporate secrets to sensitive government and infrastructure systems. At the personal level, a breach into Under Armour’s MyFitnessPal health tracker accounts resulted in the theft of private data from an estimated 150 million people.

So, what can we expect on the cyber security front in the coming year? Here are some of the trends and activities most likely to affect organizations, governments, and individuals in 2019 and beyond.

Read More »