Main Menu
  • COMPANY
    • Boundless Cybersecurity
    • Press Releases
    • News
    • Events
    • Awards
    • Leadership
    • Press Kit
    • Careers
  • PROMOTIONS
    • SonicWall Promotions
    • Customer Loyalty Program
  • MANAGED SERVICES
    • Managed Security Services
    • Security as a Service
    • Professional Services
SonicWall
  • Products
      All Products A–Z
      Free Trials
    • Network Security
      • Next-Generation Firewall (NGFW)
      • Network Security Services
      • Network Security Management
      • Secure SD-WAN
    • Threat Protection
      • Advanced Threat Protection Cloud
      • Advanced Threat Protection Appliance
      • Capture Labs
    • Secure Access Service Edge (SASE)
      • Zero-Trust Network Access (ZTNA)
    • Cloud Security
      • Cloud Firewall
      • Cloud App Security
    • Endpoint Security
      • Endpoint Detection & Response (EDR)
    • Email Security
      • Cloud Email Security
      • Hosted Email Security
      • On-Prem Email Security
    • Secure Access
      • Wireless Access Points
      • Network Switch
      • Virtual Private Network (VPN)
    • Wi-Fi 6 Access Points

      SonicWall SonicWave 600 series access points provide always-on, always-secure connectivity for complex, multi-device environments.

      Read More
  • Solutions
    • Industries
      • Distributed Enterprises
      • Retail & Hospitality
      • K-12 Education
      • Higher Education
      • State & Local
      • Federal
      • Healthcare
      • Financial Services
      • Carriers
    • Use Cases
      • Secure SD-Branch
      • Network Segmentation
      • Zero Trust Security
      • Secure SD-WAN
      • Office 365 Security
      • SaaS Security
      • Secure Wi-Fi
    • Solutions Widgets
      • Solutions Content Widgets
        Federal

        Protect Federal Agencies and Networks with scalable, purpose-built cybersecurity solutions

      • Solutions Image Widgets
  • Partners
    • SonicWall Partners
      • Partners Overview
      • Find a Partner
      • Authorized Distributors
      • Technology Partners
    • Partner Resources
      • Become a Partner
      • SonicWall University
      • Training & Certification
    • Partner Widgets
      • Custom HTML : Partners Content WIdgets
        Partner Portal

        Access to deal registration, MDF, sales and marketing tools, training and more

      • Partners Image Widgets
  • Support
    • Support
      • Support Portal
      • Knowledge Base
      • Technical Documentation
      • Community
      • Video Tutorials
      • Product Life Cycle Tables
      • Partner Enabled Services
      • Contact Support
    • Resources
      • Resource Center
      • Events
      • Free Trials
      • Blog
      • SonicWall University
      • MySonicWall
    • Capture Labs
      • Capture Labs
      • Security Center
      • Security News
      • PSIRT
      • Application Catalog
    • Support Widget
      • Custom HTML : Support Content WIdgets
        Support Portal

        Find answers to your questions by searching across our knowledge base, community, technical documentation and video tutorials

      • Support Image Widgets
  • COMPANY
    • Boundless Cybersecurity
    • Press Releases
    • News
    • Events
    • Awards
    • Leadership
    • Press Kit
    • Careers
  • PROMOTIONS
    • SonicWall Promotions
    • Customer Loyalty Program
  • MANAGED SERVICES
    • Managed Security Services
    • Security as a Service
    • Professional Services
  • Contact Sales
  • English English English en
  • BLOG
  • CONTACT SALES
  • FREE TRIALS
  • English English English en
SonicWall
  • Products
      All Products A–Z
      Free Trials
    • Network Security
      • Next-Generation Firewall (NGFW)
      • Network Security Services
      • Network Security Management
      • Secure SD-WAN
    • Threat Protection
      • Advanced Threat Protection Cloud
      • Advanced Threat Protection Appliance
      • Capture Labs
    • Secure Access Service Edge (SASE)
      • Zero-Trust Network Access (ZTNA)
    • Cloud Security
      • Cloud Firewall
      • Cloud App Security
    • Endpoint Security
      • Endpoint Detection & Response (EDR)
    • Email Security
      • Cloud Email Security
      • Hosted Email Security
      • On-Prem Email Security
    • Secure Access
      • Wireless Access Points
      • Network Switch
      • Virtual Private Network (VPN)
    • Wi-Fi 6 Access Points

      SonicWall SonicWave 600 series access points provide always-on, always-secure connectivity for complex, multi-device environments.

      Read More
  • Solutions
    • Industries
      • Distributed Enterprises
      • Retail & Hospitality
      • K-12 Education
      • Higher Education
      • State & Local
      • Federal
      • Healthcare
      • Financial Services
      • Carriers
    • Use Cases
      • Secure SD-Branch
      • Network Segmentation
      • Zero Trust Security
      • Secure SD-WAN
      • Office 365 Security
      • SaaS Security
      • Secure Wi-Fi
    • Solutions Widgets
      • Solutions Content Widgets
        Federal

        Protect Federal Agencies and Networks with scalable, purpose-built cybersecurity solutions

      • Solutions Image Widgets
  • Partners
    • SonicWall Partners
      • Partners Overview
      • Find a Partner
      • Authorized Distributors
      • Technology Partners
    • Partner Resources
      • Become a Partner
      • SonicWall University
      • Training & Certification
    • Partner Widgets
      • Custom HTML : Partners Content WIdgets
        Partner Portal

        Access to deal registration, MDF, sales and marketing tools, training and more

      • Partners Image Widgets
  • Support
    • Support
      • Support Portal
      • Knowledge Base
      • Technical Documentation
      • Community
      • Video Tutorials
      • Product Life Cycle Tables
      • Partner Enabled Services
      • Contact Support
    • Resources
      • Resource Center
      • Events
      • Free Trials
      • Blog
      • SonicWall University
      • MySonicWall
    • Capture Labs
      • Capture Labs
      • Security Center
      • Security News
      • PSIRT
      • Application Catalog
    • Support Widget
      • Custom HTML : Support Content WIdgets
        Support Portal

        Find answers to your questions by searching across our knowledge base, community, technical documentation and video tutorials

      • Support Image Widgets
  • COMPANY
    • Boundless Cybersecurity
    • Press Releases
    • News
    • Events
    • Awards
    • Leadership
    • Press Kit
    • Careers
  • PROMOTIONS
    • SonicWall Promotions
    • Customer Loyalty Program
  • MANAGED SERVICES
    • Managed Security Services
    • Security as a Service
    • Professional Services
  • Contact Sales
  • Menu

Unable to access City or State Sponsored Sites Behind a SonicWall firewall

03/26/2020 682 People found this article helpful 195,492 Views

    Download
    Print
    Share
    • LinkedIn
    • Twitter
    • Facebook
    • Email
    • Copy URL The link has been copied to clipboard

    Description

    Unable to access City or State Sponsored sites behind a SonicWall firewall

    Resolution

    Lately, users in certain localities have discovered that they no longer have access to certain city and state sponsored government-related sites, regardless of whether or not security services are enabled.

    A packet capture will reveal that all packets are being forwarded, and yet the connection is not being established. Further scrutiny of the capture shows that although the SYN packet is being appropriately forwarded to the site, the initiator does NOT receive a SYN/ACK packet in response... merely an ACK packet, which violates the TCP handshake (SYN  >  SYN/ACK  > ACK).

    As it turns out, the affected responses indicate that connections which follow the RFC 6528 to defend against Sequence Number Attacks, a method by which an attacker may interject themselves into a connection (Also known as a Man-In-The-Middle, or MITM attack), are being rejected.  Without the security measure the SonicWall puts in place as per the aforementioned RFC, an attacker may obtain ALL information passed between the two parties. However, WITH the security measure in place, no response is received.

    RFC 6528 explains the need for TCP Sequence Randomization thusly:

     "An eavesdropper who can observe the initial messages for a connection can determine its sequence number state, and may still be able to launch sequence number guessing attacks by impersonating that connection. However, such an eavesdropper can also hijack existing connections [Joncheray1995], so the incremental threat is not that high. Still, since the offset between a fake connection and a given real connection will be more or less constant for the lifetime of the secret, it is important to ensure that attackers can never capture such packets. Typical attacks that could disclose them include both eavesdropping and the variety of routing attacks discussed in [Bellovin1989].  "Off-path attacks against TCP connections require the attacker to guess or know the four-tuple (localip, localport, remoteip, remoteport) that identifies the target connection. TCP port number randomization [RFC6056] reduces the chances of an attacker of guessing such a four-tuple by obfuscating the selection of TCP ephemeral ports, therefore contributing to the mitigation of such attacks..." 


    This phenomenon, where users behind a secure SonicWall are unable to reach an affected site, has been observed recently with a number of city and state-sponsored sites.  At this time, the only known options are limited to the following options:

    1.) Disable TCP Sequence Randomization on the firewall that is keeping the connection secure, or else
    2.) Allow communication with the affected sites to fail until the site responds in an RFC compliant manner.

    DISABLING TCP SEQUENCE RANDOMIZATION IS **NOT** RECOMMENDED BY SonicWall, AND CAN RESULT IN AN ATTACKER OBTAINING ALL DATA PASSED BETWEEN LOCATIONS.

    Traffic to city and government sites within the US and the UK has recently been diverted to foreign countries by means of BGP configuration.  Allowing TCP Sequence randomization while traffic is being diverted may allow both local and foreign entities to view all traffic passed.  This information is referenced in the following articles.

    http://arstechnica.com/security/2013/11/repeated-attacks-hijack-huge-chunks-of-internet-traffic-researchers-warn/

    http://arstechnica.com/security/2015/03/mysterious-snafu-hijacks-uk-nukes-makers-traffic-through-ukraine/

    If, despite the known risk of allowing an attacker to obtain all data, it is still desired to navigate to an affected site in a manner that is not RFC compliant, the following steps can be taken to disable TCP Sequence Randomization on the SonicWall NGFW:

    Workaround:

    Step 1:  Navigate to the /diag.html page of the firewall (located at https:///diag.html) and click the "Internal Settings" button
    Step 2:  In the "Routing and Network Settings" section,
    Disable the checkbox "Enable TCP sequence number randomization".
    Step 3: 
    Click "Accept".  Click "Close" on the left to return to the UI.


    How to Test:

    Attempt to access the site from behind the firewall.  You may also run another packet capture to ensure that after two or three (SYN  >  ACK) attempts, a SYN/ACK packet is finally provided in response completing the (SYN  >  SYN/ACK  >  ACK) handshake.

     

    Related Articles

    • How to Setup the SonicWave 600 series
    • Identical Access Rules for different users/user groups
    • Advanced Network Security eLearning Training Course

    Categories

    • Firewalls > TZ Series
    • Firewalls > SonicWall SuperMassive E10000 Series
    • Firewalls > SonicWall SuperMassive 9000 Series
    • Firewalls > SonicWall NSA Series

    Not Finding Your Answers?

    ASK THE COMMUNITY

    Was This Article Helpful?

    YESNO

    Article Helpful Form

    Article Not Helpful Form

    Company
    • Careers
    • News
    • Leadership
    • Awards
    • Press Kit
    • Contact Us
    Popular resources
    • Communities
    • Blog
    • SonicWall Capture Labs

    Stay In Touch

    • By submitting this form, you agree to our Terms of Use and acknowledge our Privacy Statement. You can unsubscribe at any time from the Preference Center.
    • This field is for validation purposes and should be left unchanged.
    • Facebook
    • Twitter
    • Linkedin
    • Youtube
    • Instagram

    © 2023 SonicWall. All Rights Reserved.

    • Legal
    • Privacy
    • English
    Scroll to top