Kmizra LLC v. Citrix Systems Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: K.Mizra LLC (Delaware)
  • Defendant: Citrix Systems, Inc. (Delaware); Cloud Software Group, Inc. (Delaware)
  • Plaintiff’s Counsel: Gelber Schachter & Greenberg, P.A.; Sheridan Ross P.C.
• Case Identification: 0:25-cv-60803, S.D. Fla., 04/24/2025
• Venue Allegations: Venue is asserted based on Defendants having their principal place of business and corporate headquarters within the Southern District of Florida.
• Core Dispute: Plaintiff alleges that Defendant’s Secure Private Access solution, a zero-trust network access product, infringes a patent related to methods for detecting, quarantining, and remediating potentially insecure computers attempting to connect to a protected network.
• Technical Context: The technology addresses network security challenges arising from mobile and bring-your-own-device (BYOD) computing, where devices frequently connect to untrusted networks and may carry threats back to a protected corporate environment.
• Key Procedural History: The complaint notes that the asserted patent previously survived an Inter Partes Review (IPR) proceeding, where the Patent Trial and Appeal Board (PTAB) issued a Final Written Decision finding the challenged claims not unpatentable. While this decision was appealed and remanded by the Federal Circuit on procedural grounds, the IPR was subsequently dismissed by the PTAB at the parties' request.

Case Timeline

Date	Event
2004-09-27	Priority Date for U.S. Patent No. 8,234,705
2012-07-31	U.S. Patent No. 8,234,705 Issued
2022-08	Plaintiff allegedly first contacted Defendant regarding potential infringement
2023-04	Plaintiff allegedly followed up on initial contact with Defendant
2025-01-31	Plaintiff allegedly sent a letter with a claim chart to Defendant
2025-04-24	Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,234,705 - "Contagion Isolation and Inoculation"

• Patent Identification: U.S. Patent No. 8,234,705, "Contagion Isolation and Inoculation", issued July 31, 2012.

The Invention Explained

• Problem Addressed: The patent identifies a security threat posed by mobile computers (e.g., laptops) that connect to untrusted public networks, where they can become infected with viruses, worms, or other malware. When these devices subsequently attempt to reconnect to a protected enterprise network, they risk spreading the "contagion" before security measures can detect and prevent the harm (’705 Patent, col. 1:15-41).
• The Patented Solution: The invention provides a system that intercepts a host computer's connection request to a protected network. It determines if the host needs to be quarantined, and if so, grants only limited network access. This limited access prevents communication with other protected hosts but allows the quarantined host to connect to specific "remediation" resources (e.g., an update server) to download patches or undergo scans to resolve the security issue, after which full access can be granted (’705 Patent, Abstract; col. 3:7-22).
• Technical Importance: This approach provides an automated, intermediate security state between full network access and complete denial, specifically addressing the risk from transient, potentially compromised devices in an enterprise environment (Compl. ¶¶24, 26).

Key Claims at a Glance

• The complaint asserts independent claim 19 (Compl. ¶27).
• The essential elements of independent claim 19 include:
  • A computer program product for detecting an insecure condition on a "first host" attempting to connect to a protected network.
  • Detection involves contacting a "trusted computing base" associated with a "trusted platform module" (TPM) on the host.
  • Detection further involves receiving a response and determining if it includes a "valid digitally signed attestation of cleanliness."
  • The attestation must certify that the host is not infested and/or that a specific patch or patch level is present.
  • If the attestation is not valid, the host is quarantined by preventing it from sending data to other hosts on the protected network.
  • Quarantining includes serving a "quarantine notification page" for web requests and, for DNS queries, providing the IP address of a "quarantine server" if the queried host is not a remediation host.
  • Finally, the product permits the quarantined host to communicate with a "remediation host" to remedy the insecure condition.
• The complaint reserves the right to assert additional dependent and independent claims (Compl. ¶27).

III. The Accused Instrumentality

Product Identification

• The complaint names "Citrix's Secure Private Access (SPA) solution," including its cloud and on-premises implementations (Compl. ¶39).

Functionality and Market Context

• The SPA solution is described as a zero-trust network access (ZTNA) product that provides secure, adaptive access to corporate applications (Compl. ¶47). A core feature is the "Device Posture" service, which scans an end-user device to ensure it meets predefined security criteria before being granted access to the protected network (Compl. ¶48).
• The complaint alleges the SPA solution functions by defining policies to check endpoint device posture. Based on the compliance status, the service can deny access or provide restricted or full access to applications (Compl. ¶¶48, 52). The complaint also describes the SPA solution’s ability to integrate with third-party services like Microsoft Intune, which allegedly uses a device's Trusted Platform Module (TPM) for enrollment attestation (Compl. ¶49). The diagram provided in the complaint illustrates the SPA solution acting as a gatekeeper between end-user devices and internal applications, using factors like device posture to make access decisions (Compl. p. 15).

IV. Analysis of Infringement Allegations

’705 Patent Infringement Allegations

| Claim Element (from Independent Claim 19) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
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| [A] detecting an insecure condition on a first host that has connected or is attempting to connect to a protected network | The Citrix SPA solution uses its "Device Posture service" to scan end-user devices before establishing a session to detect insecure conditions based on compliance with defined policies. | ¶48 | col. 22:14-17 |
| [B1] contacting a trusted computing base associated with a trusted platform module within the first host | The SPA solution allegedly integrates with Microsoft Intune, which in turn relies on the device's Trusted Platform Module (TPM) to store certificate keys and perform attestation during enrollment. | ¶49 | col. 22:19-22 |
| [B2] receiving a response, and determining whether the response includes a valid digitally signed attestation of cleanliness | The SPA solution allegedly receives and evaluates the results of the device posture scan, which is based on the Windows enrollment attestation process that relies on TPM-stored keys. | ¶50 | col. 22:23-26 |
| [C] wherein the valid digitally signed attestation of cleanliness includes at least one of an attestation that the trusted computing base has ascertained that the first host is not infested, and an attestation that the trusted computing base has ascertained the presence of a patch or a patch level... | The SPA solution allegedly allows administrators to enforce access controls based on device attributes such as Operating System (OS) version, which corresponds to patch level, and other security data. A provided table shows checks for OS version and antivirus status (Compl. p. 22). | ¶51 | col. 22:27-33 |
| [D] when it is determined that the response does not include a valid digitally signed attestation of cleanliness, quarantining the first host... | If a device is found to be non-compliant with security policies, the SPA solution quarantines the device by denying access to corporate resources. A diagram in the complaint depicts this "Denied Login Use Case" (Compl. p. 24). | ¶52 | col. 22:34-38 |
| [E1] ...serving a quarantine notification page to the first host when the service request comprises a web server request | When a non-compliant device is denied access, the SPA solution allegedly provides a customizable notification page informing the user of the access denial. A screenshot shows an example "Access denied" page (Compl. p. 26). | ¶53 | col. 22:40-43 |
| [E2] ...in the event the service request comprises a DNS query, providing in response an IP address of a quarantine server configured to serve the quarantine notification page... | The complaint alleges that the Accused Instrumentalities meet this limitation, but does not provide specific factual allegations detailing the DNS redirection mechanism. | ¶54 | col. 22:44-49 |
| [F] permitting the first host to communicate with the remediation host. | The SPA solution is alleged to provide for continuous monitoring and dynamic access control, which allows for access to be granted or adjusted, thereby permitting communication to remedy an insecure condition. | ¶55 | col. 22:47-49 |

• Identified Points of Contention:
  • Scope Questions: A central question may be whether the term "trusted computing base," as used in the patent, can be construed to cover an architecture that relies on integration with a separate, third-party service (Microsoft Intune) to interact with a device's TPM, as the complaint alleges.
  • Technical Questions: The complaint's allegations for element [E2], concerning the redirection of DNS queries to a quarantine server, appear less detailed than for other elements. Given the noted importance of this limitation in the prior IPR proceeding (Compl. ¶36), the evidentiary basis for how the SPA product performs this specific function will likely be a point of significant dispute. A further question is whether the "Device Posture" checks, which evaluate policy compliance, are technically and functionally the same as the claimed "valid digitally signed attestation of cleanliness" originating from a TPM.

V. Key Claim Terms for Construction

• The Term: "trusted computing base"

• Context and Importance: This term is foundational to the infringement theory, as it defines the entity that performs the core attestation function. Practitioners may focus on this term because the complaint's theory relies on an integration between the accused Citrix product and a third-party service (Microsoft Intune) to satisfy the limitation. The dispute will likely center on whether the "trusted computing base" must be a singular, integrated component as might be described in the patent's embodiments, or if it can encompass a distributed system of cooperating services.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The claim language requires the base to be "associated with a trusted platform module" (’705 Patent, col. 22:20-22), which does not explicitly forbid that association from occurring via a third-party software bridge or API.
  • Evidence for a Narrower Interpretation: The patent specification describes a "trusted computing base within a computer" as part of the "Paladium security initiative" (’705 Patent, col. 13:5-9), language that could be used to argue for an interpretation requiring a more tightly integrated component within the host system itself.

• The Term: "quarantine server"

• Context and Importance: The functionality of the "quarantine server", particularly its role in handling DNS queries (claim 19[E2]), was identified in the complaint as a key issue in prior PTAB proceedings (Compl. ¶36). Its construction will be critical because the defendant will likely challenge whether the accused product's general access-denial mechanism includes the specific DNS-redirection function required by the claim.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The patent describes the quarantine server's function as providing "information and links to assist in remediation" and notes this can be accomplished "in numerous ways, for example by providing an alternate DNS service" (’705 Patent, col. 15:1-6). This may suggest the function is more important than the specific implementation.
  • Evidence for a Narrower Interpretation: Claim 19[E2] recites a specific mechanism: "providing in response an IP address of a quarantine server" to a DNS query. This explicit recitation of a DNS-level response could be argued to limit the scope to systems that perform this exact function, as opposed to systems that achieve a similar result through other means like HTTP redirects.

VI. Other Allegations

• Indirect Infringement: The complaint alleges active inducement of infringement under 35 U.S.C. § 271(b). The factual basis asserted is that Citrix encourages and instructs its customers, through promotion, advertising, and user manuals, to install and use the Accused Instrumentalities in a manner that directly infringes the ’705 Patent (Compl. ¶56).
• Willful Infringement: The willfulness allegation is based on alleged knowledge of the ’705 Patent. The complaint asserts that Citrix had actual knowledge "no later than January 31, 2025," the date it allegedly received a letter containing a claim chart. The complaint also references earlier contacts in August 2022 and April 2023 as evidence of knowledge (Compl. ¶¶40-41, 56).

VII. Analyst’s Conclusion: Key Questions for the Case

• A core issue will be one of definitional scope: can the term "trusted computing base", which the patent links to security initiatives like Palladium, be construed to cover the accused system’s architecture, which relies on a third-party cloud service (Microsoft Intune) to interface with the host's TPM?
• A second central question will be one of evidentiary proof: what evidence will emerge in discovery to demonstrate that the accused SPA solution performs the specific DNS-level redirection to a "quarantine server" as required by claim 19[E2], a limitation that was previously a focal point of validity challenges?
• Finally, the case may turn on a question of functional operation: does the accused SPA solution's "Device Posture" check, which verifies compliance with administrative policies (e.g., OS version), operate in substantially the same way as the claimed "valid digitally signed attestation of cleanliness" generated by a TPM, or is there a fundamental mismatch in their technical function and security guarantees?