Patent Publication Number: US-2022239484-A1

Title: Detection of Compromised Credentials

Description:
BACKGROUND 
     The disclosure relates generally to network security and, more specifically to detecting compromised credentials corresponding to a client to prevent unauthorized access to protected resources hosted by resource servers connected to a network. 
     Identity and access management (TAM) is a framework of processes, policies, and technologies that facilitates the management of digital identities. An TAM framework can control user access to protected resources (e.g., data, documents, files, software, hardware, services, and the like) corresponding to an entity, such as, for example, an enterprise, business, company, organization, institution, agency, or the like. TAM systems can be deployed on-premises, provided by a third-party vendor through a cloud-based subscription model, or deployed in a hybrid model. Typical systems used for TAM include single sign-on systems, two-factor authentication, multifactor authentication, privileged access management, and token-based authorization. 
     Token-based authentication (e.g., OAuth 2.0) is a protocol that allows users to verify their identity and, in return receive a unique access token. During the lifetime of an access token (i.e., a defined period of time), users can access a protected resource, such as a cloud service, for which the access token has been issued for. First, a user requests access to the protected resource. That may involve a login with credentials, such as username and password. Typically, the authorization server determines whether the user should have access by, for example, comparing the received credentials with stored credentials corresponding to the user. After credential authentication or verification, the authorization server issues the access token to the user. 
     SUMMARY 
     According to one illustrative embodiment, a computer-implemented method for managing client access token requests is provided. A computer determines whether a current time interval between a last allowed access token request matches a regular access token request interval for a client. In response to the computer determining that the current time interval does match the regular access token request interval for the client, the computer allows a current access token request. The computer generates an access token for the client to access a protected resource hosted by a resource server based on allowing the current access token request. The computer issues the access token to the client via a network. According to other illustrative embodiments, a computer system and computer program product for managing client access token requests are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial representation of a network of data processing systems in which illustrative embodiments may be implemented; 
         FIG. 2  is a diagram of a data processing system in which illustrative embodiments may be implemented; 
         FIG. 3  is a diagram illustrating an example of client access token request validation in accordance with an illustrative embodiment; and 
         FIGS. 4A-4B  are a flowchart illustrating a process for managing client access token requests in accordance with an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer-readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure. 
     The computer-readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer-readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer-readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer-readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer-readable program instructions described herein can be downloaded to respective computing/processing devices from a computer-readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network, and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the respective computing/processing device. 
     Computer-readable program instructions for carrying out operations of the present disclosure may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object-oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer, and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer-readable program instructions by utilizing state information of the computer-readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure. 
     Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
     These computer-readable program instructions may be provided to a processor of a computer or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer-readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer-implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be accomplished as one step, executed concurrently, substantially concurrently, in a partially or wholly temporally overlapping manner, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     With reference now to the figures, and in particular, with reference to  FIG. 1  and  FIG. 2 , diagrams of data processing environments are provided in which illustrative embodiments may be implemented. It should be appreciated that  FIG. 1  and  FIG. 2  are only meant as examples and are not intended to assert or imply any limitation regarding the environments in which different embodiments may be implemented. Many modifications to the depicted environments may be made. 
       FIG. 1  depicts a pictorial representation of a network of data processing systems in which illustrative embodiments may be implemented. Network data processing system  100  is a network of computers, data processing systems, and other devices in which the illustrative embodiments may be implemented. Network data processing system  100  contains network  102 , which is the medium used to provide communications links between the computers, data processing systems, and other devices connected together within network data processing system  100 . Network  102  may include connections, such as, for example, wire communication links, wireless communication links, fiber optic cables, and the like. 
     In the depicted example, resource server  104  and authorization server  106  connect to network  102 , along with storage  108 . Resource server  104  and authorization server  106  may be, for example, server computers with high-speed connections to network  102 . Also, it should be noted that resource server  104  and authorization server  106  may each represent multiple computing nodes in one or more cloud environments managed by one or more entities. Alternatively, resource server  104  and authorization server  106  may each represent one or more clusters of servers in one or more data centers. 
     Resource server  104  hosts a set of protected resources. The set of protected resources may include, for example, at least one of data, documents, files, software, hardware, services, and the like. Resource server  104  is capable of accepting and responding to protected resource access requests from client devices using access tokens. Access tokens contain client identifiers for network sessions and identify protected resource access privileges. 
     Authorization server  106  issues the access tokens to the client devices after successfully authenticating credentials corresponding to the client devices. Furthermore, authorization server  106  detects when client credentials have been compromised, preventing unauthorized access to the set of protected resources hosted by the resource server  104  by determining whether a current access token request was performed by a client within a regular time interval for such client access token requests. The regular time interval is an expected interval of time by authorization server  106  to receive the access token request from the client within a configurable time window of the error to account for network jitter and the like. If the client does not perform the access token request at the expected interval of time (i.e., a consistent, regular time interval), then authorization server  106  denies the access token request, determines that client credentials have been compromised, and notifies the client owner or administrator regarding the compromised credentials for appropriate action. In addition, the authorization server  106  instructs resource server  104  to deny access to the set of protected resources by the client. If the client does perform the access token request at the expected regular interval of time, then authorization server  106  allows the access token request, generates the access token for the client, issues the access token to the client to access the set of protected resources hosted by the resource server  104 , and instructs resource server  104  to grant access to the set of protected resources by the client. 
     Client  110 , client  112 , and client  114  also connect to network  102 . Clients  110 ,  112 , and  114  are clients of resource server  104 . In this example, clients  110 ,  112 , and  114  are shown as desktop or personal computers with wire communication links to network  102 . However, it should be noted that clients  110 ,  112 , and  114  are examples only and may represent other types of data processing systems, such as, for example, network computers, laptop computers, handheld computers, smartphones, smartwatches, smart televisions, smart vehicles, smart glasses, smart appliances, gaming devices, kiosks, and the like, with wired or wireless communication links to network  102 . Users of clients  110 ,  112 , and  114  may utilize specific web applications loaded on clients  110 ,  112 , and  114  to access corresponding protected resources hosted by the resource server  104  using access tokens from the authorization server  106  after successful authentication and authorization by authorization server  106 . 
     Storage  108  is a network storage device capable of storing any type of data in a structured format or an unstructured format. In addition, storage  108  may represent a plurality of network storage devices. Further, storage  108  may store identifiers, and network addresses for a plurality of resource servers, identifiers, and network addresses for a plurality of client devices, identifiers for a plurality of client device users, and the like. Furthermore, storage  108  may store other types of data, such as credential data that may include usernames, passwords, and biometric data associated with the client device users, for example. 
     In addition, it should be noted that network data processing system  100  may include any number of additional servers, clients, storage devices, and other devices not shown. Program code located in network data processing system  100  may be stored on a computer-readable storage medium or a set of computer-readable storage media and downloaded to a computer or other data processing device for use. For example, program code may be stored on a computer-readable storage medium on resource server  104  and downloaded to client  110  over network  102  for use on client  110 . 
     In the depicted example, network data processing system  100  may be implemented as a number of different types of communication networks, such as, for example, an internet, an intranet, a wide area network (WAN), a local area network (LAN), a telecommunications network, or any combination thereof.  FIG. 1  is intended as an example only and not as an architectural limitation for the different illustrative embodiments. 
     As used herein, when used with reference to items, “a number of” means one or more of the items. For example, “a number of different types of communication networks” is one or more different types of communication networks. Similarly, “a set of,” when used with reference to items, means one or more of the items. 
     Further, the term “at least one of,” when used with a list of items, means different combinations of one or more of the listed items may be used, and only one of each item in the list may be needed. In other words, “at least one of” means any combination of items and number of items may be used from the list, but not all of the items in the list are required. The item may be a particular object, a thing, or a category. 
     For example, without limitation, “at least one of item A, item B, or item C” may include item A, item A and item B, or item B. This example may also include item A, item B, and item C or item B and item C. Of course, any combinations of these items may be present. In some illustrative examples, “at least one of” may be, for example, without limitation, two of item A; one of item B; and ten of item C; four of item B and seven of item C; or other suitable combinations. 
     With reference now to  FIG. 2 , a diagram of a data processing system is depicted in accordance with an illustrative embodiment. Data processing system  200  is an example of a computer, such as authorization server  106  in  FIG. 1 , in which computer-readable program code or instructions implementing the access token management processes of illustrative embodiments may be located. In this example, the data processing system  200  includes communications fabric  202 , which provides communications between processor unit  204 , memory  206 , persistent storage  208 , communications unit  210 , input/output (I/O) unit  212 , and display  214 . 
     Processor unit  204  serves to execute instructions for software applications and programs that may be loaded into memory  206 . Processor unit  204  may be a set of one or more hardware processor devices or may be a multi-core processor, depending on the particular implementation. 
     Memory  206  and persistent storage  208  are examples of storage devices  216 . As used herein, a computer-readable storage device or a computer-readable storage medium is any piece of hardware that is capable of storing information, such as, for example, without limitation, data, computer-readable program code in functional form, and/or other suitable information either on a transient basis or a persistent basis. Further, a computer-readable storage device or a computer-readable storage medium excludes a propagation medium, such as transitory signals. Furthermore, a computer-readable storage device or a computer-readable storage medium may represent a set of computer-readable storage devices or a set of computer-readable storage media. Memory  206 , in these examples, may be, for example, a random-access memory (RAM) or any other suitable volatile or non-volatile storage device, such as a flash memory. Persistent storage  208  may take various forms, depending on the particular implementation. For example, persistent storage  208  may contain one or more devices. For example, persistent storage  208  may be a disk drive, a solid-state drive, a rewritable optical disk, a rewritable magnetic tape, or some combination of the above. The media used by persistent storage  208  may be removable. For example, a removable hard drive may be used for persistent storage  208 . 
     In this example, persistent storage  208  stores access token manager  218 . However, it should be noted that even though access token manager  218  is illustrated as residing in persistent storage  208 , in an alternative illustrative embodiment, access token manager  218  may be a separate component of the data processing system  200 . For example, access token manager  218  may be a hardware component coupled to communication fabric  202  or a combination of hardware and software components. 
     Access token manager  218  controls the process of detecting compromised client credentials to prevent unauthorized access to protected resources hosted by one or more resource servers connected to a network, such as, for example, network  102  in  FIG. 1 . Client  220  represents an identifier of an authorized client, such as, for example, client  110  in  FIG. 1 . Client  220  utilizes access token  222  to access a set of protected resources of a resource server, such as, for example, resource server  104  in  FIG. 1 . 
     Access token manager  218  issued access token  222  to client  220  after allowing a previous access token request performed by client  220  upon verification of credentials presented by client  220 . Access token  222  has a fixed lifetime (i.e., expiration  224 ). Expiration  224  defines a time when access token  222  is no longer valid or usable to access the set of protected resources hosted by the resource server. Access token manager  218  informed client  220  of expiration  224  upon issuance of access token  222  so that client  220  knows when access token  222  will expire. 
     At expiration  224  or at a time just prior to expiration  224  within a client-defined time threshold, client  220  performs current access token request  226 . Access token manager  218  receives current access token request  226  and notes timestamp  228  of current access token request  226 . Timestamp  228  represents when client  220  performed current access token request  226 . Previous access token request  230  represents the allowed access token request performed by client  220  above to receive access token  222 . Timestamp  232 , which was recorded by access token manager  218 , corresponds to when client  220  performed previous access token request  230 . 
     Access token manager  218  retrieves timestamp  232  corresponding to previous access token request  230  and compares timestamp  232  with timestamp  228 , which corresponds to current access token request  226 , to determine the current time interval  234 . The current time interval  234  represents the span of time between the performance of previous access token request  230  and the performance of current access token request  226  by client  220 . Current time interval  234  may be “N” number of seconds, minutes, hours, days, or the like. 
     In addition, access token manager  218  retrieves regular time interval  236 . Regular time interval  236  is a consistent period of time that elapses between each respective access token request performed by client  220 . Access token manager  218  previously determined regular time interval  236  based on one or more previously performed access token requests by client  220  and expects the time interval between access token requests performed by client  220  to be the same or substantially the same within configurable time window  238 . Configurable time window  238  is an adjustable period of time, which allows for network transmission issues, such as, for example, jitter, latency, and the like. Access token manager  218  may automatically adjust configurable time window  238 . Alternatively, a network administrator, for example, may manually adjust configurable time window  238 . 
     Access token manager  218  compares the current time interval  234  with the regular time interval  236 . If access token manager  218  determines that current time interval  234  matches regular time interval  236  within configurable time window  238  based on the comparison, then access token manager  218  allows current access token request  226 , generates new access token  240 , issues a new access token  240  to client  220 , and instructs the resource server to grant access to the set of protected resources by client  220 . The client then uses the new access token  240  to continue to access the set of resources hosted by the resource server. However, if access token manager  218  determines that current time interval  234  does not match regular time interval  236  within configurable time window  238  based on the comparison, then access token manager  218  determines that credentials corresponding to client  220  have been compromised, denies current access token request  226 , and automatically performs action steps  242 . Action steps  242  may include, for example, at least one of sending a notification to an owner or administrator of client  220  that current access token request  226  has been denied, instructing the resource server to deny access to the set of resources by client  220 , locking client  220 , revoking access tokens issued to client  220 , disabling all access tokens corresponding to client  220 , notifying network security, and the like. 
     As a result, the data processing system  200  operates as a special purpose computer system in which access token manager  218  in the data processing system  200  enables management of access token issuance by detecting compromised client credentials to prevent unauthorized access to protected network resources. In particular, access token manager  218  transforms data processing system  200  into a special purpose computer system as compared to currently available general computer systems that do not have access token manager  218 . 
     Communications unit  210 , in this example, provides for communication with other computers, data processing systems, and devices via a network, such as a network  102  in  FIG. 1 . Communications unit  210  may provide communications using both physical and wireless communications links. The physical communications link may utilize, for example, a wire, cable, universal serial bus, or any other physical technology to establish a physical communications link for data processing system  200 . The wireless communications link may utilize, for example, shortwave, high frequency, ultrahigh frequency, microwave, wireless fidelity (Wi-Fi), Bluetooth® technology, global system for mobile communications (GSM), code division multiple access (CDMA), second-generation (2G), third-generation (3G), fourth-generation (4G), 4G Long Term Evolution (LTE), LTE Advanced, fifth-generation (5G), or any other wireless communication technology or standard to establish a wireless communications link for data processing system  200 . 
     Input/output unit  212  allows for the input and output of data with other devices that may be connected to the data processing system  200 . For example, input/output unit  212  may provide a connection for user input through a keypad, a keyboard, a mouse, a microphone, and/or some other suitable input device. Display  214  provides a mechanism to display information to a user and may include touch screen capabilities to allow the user to make on-screen selections through user interfaces or input data, for example. 
     Instructions for the operating system, applications, and/or programs may be located in storage devices  216 , which are in communication with processor unit  204  through communications fabric  202 . In this illustrative example, the instructions are in a functional form on persistent storage  208 . These instructions may be loaded into memory  206  for running by processor unit  204 . The processes of the different embodiments may be performed by processor unit  204  using computer-implemented instructions, which may be located in a memory, such as memory  206 . These program instructions are referred to as program code, computer usable program code, or computer-readable program code that may be read and run by a processor in processor unit  204 . The program instructions, in the different embodiments, may be embodied on different physical computer-readable storage devices, such as memory  206  or persistent storage  208 . 
     Program code  244  is located in a functional form on computer-readable media  246  that is selectively removable and may be loaded onto or transferred to the data processing system  200  for running by processor unit  204 . Program code  244  and computer-readable media  246  form computer program product  248 . In one example, computer-readable media  246  may be computer-readable storage media  250  or computer-readable signal media  252 . 
     In these illustrative examples, computer-readable storage media  250  is a physical or tangible storage device used to store program code  244  rather than a medium that propagates or transmits program code  244 . Computer-readable storage media  250  may include, for example, an optical or magnetic disc that is inserted or placed into a drive or other device that is part of persistent storage  208  for transfer onto a storage device, such as a hard drive, that is part of persistent storage  208 . Computer-readable storage media  250  also may take the form of a persistent storage, such as a hard drive, a thumb drive, or a flash memory that is connected to data processing system  200 . 
     Alternatively, program code  244  may be transferred to the data processing system  200  using computer-readable signal media  252 . Computer-readable signal media  252  may be, for example, a propagated data signal containing program code  244 . For example, computer-readable signal media  252  may be an electromagnetic signal, an optical signal, or any other suitable type of signal. These signals may be transmitted over communication links, such as wireless communication links, an optical fiber cable, a coaxial cable, a wire, or any other suitable type of communications link. 
     Further, as used herein, “computer-readable media  246 ” can be singular or plural. For example, program code  244  can be located in computer-readable media  246  in the form of a single storage device or system. In another example, program code  244  can be located in computer-readable media  246  that is distributed in multiple data processing systems. In other words, some instructions in program code  244  can be located in one data processing system, while other instructions in program code  244  can be located in one or more other data processing systems. For example, a portion of program code  244  can be located in computer-readable media  246  in a server computer, while another portion of program code  244  can be located in computer-readable media  246  located in a set of client computers. 
     The different components illustrated for data processing system  200  are not meant to provide architectural limitations to the manner in which different embodiments can be implemented. In some illustrative examples, one or more of the components may be incorporated in or otherwise form a portion of another component. For example, memory  206 , or portions thereof, may be incorporated in processor unit  204  in some illustrative examples. The different illustrative embodiments can be implemented in a data processing system, including components in addition to or in place of those illustrated for data processing system  200 . Other components shown in  FIG. 2  can be varied from the illustrative examples shown. The different embodiments can be implemented using any hardware device or system capable of running program code  244 . 
     In another example, a bus system may be used to implement communications fabric  202  and may be comprised of one or more buses, such as a system bus or an input/output bus. Of course, the bus system may be implemented using any suitable type of architecture that provides for a transfer of data between different components or devices attached to the bus system. 
     OAuth 2.0 clients make use of a shared secret between the client (e.g., web application) and authorization server for authorization to access protected resources hosted by a resource server. The application programming interface (API) endpoints of the authorization server may be, for example, /token, /introspect, /revoke, and the like. These API endpoints of the authorization server can support a variety of authorization methods, such as, for example, JSON web token assertions, client certificates, access tokens, basic authentication, POST parameters, and the like. However, these methods vary in complexity, from the simplest, such as basic authentication and POST parameters, which just requires the client to present client credentials, to more complex methods where a cryptography certificate is used, or an assertion is created by the client. These more complex methods require increased effort, which is sometimes non-trivial for OAuth 2.0 clients to provide, such as creating signed assertions or managing certificate information. This increased complexity can be undesirable to owners and administrators of such clients. 
     Protecting the client&#39;s secret of a client is important for preventing unauthorized access to protected resources (i.e., maintaining the security of protected resources). Illustrative embodiments detect when client credentials have been compromised (e.g., misappropriated) and are being used by an unauthorized (e.g., malicious) user trying to access a protected resource (e.g., a service) using the compromised client credentials. Illustrative embodiments secure environments that utilize access tokens as an authorization method when calling authorization server API endpoints for authorization to access protected resources hosted by resource servers. An access token is shared among the authorization server, the resource server the access token is valid for, and the client the access token is issued to. 
     A client obtains an access token from an authorization server by making a client access token grant type request for the access token. The result of a successful access token request (i.e., providing valid credentials, such as, for example, correct username and password, to the authorization server) by a client is an access token having a fixed lifetime (i.e., a defined time when the access token expires and is no longer valid or usable), which the client can use to access a protected resource hosted by the resource server, along with the authorization server API endpoints mentioned above. The authorization server sets the fixed lifetime (i.e., expiration) of the access token and informs the client of the fixed lifetime so that the client knows when the access token will expire and become invalid. In one illustrative embodiment, the authorization server sets expiration for the fixed lifetime of all access tokens the same for every client. In an alternative illustrative embodiment, the authorization server sets a different expiration for access tokens for each different client. 
     Because of the known expiration (i.e., fixed lifetime) of an access token, the authorization server can predict the regularity of, or time interval between, access token requests by a client. The authorization server leverages this expected pattern of access token requests by a client to detect deviations from this expected pattern of client behavior, which is indicative of an invalid or unauthorized access token request (i.e., compromised credentials). 
     Illustrative embodiments can be utilized by an entity, such as, for example, an enterprise, company, business, organization, institution, agency, or the like, that has authorization policies requiring a client to utilize an access token to access any of the entity&#39;s authorization server API endpoints. For a client to access these authorization API endpoints, the client must perform an access token request with the authorization server at regular or consistent time intervals (i.e., at substantially the same interval of time within a configurable window of time (e.g., five seconds) to allow for network delays caused by, for example, jitter). The regular interval is attained via the client running logic or a thread in the background that generates a new access token request when the expiration of a current access token is approaching within a client-defined threshold period of time. For example, an application developer creates a web application with the logic that generates an access token request every “N” time interval, where N is a number of seconds, minutes, hours, or the like. Alternatively, the regular interval is attained via the client having the load at such a level that when an access token is approaching its expiration, the client performs a new access token request within a defined timeout (e.g., the client is invoked every five seconds with regular load). 
     A client using either of these mechanisms above will perform an access token request at the regular time interval (i.e., an expected interval of time by the authorization server). Consequently, the authorization server tracks when a client performs an access token request and determines whether the access token request falls within the expected or historical pattern of access token requests by the client. In other words, the authorization server correlates the current client access token request with one or more historical or past client access token requests and evaluates the regularity of, or the time interval between, these client access token requests to ensure that the current client access token request falls within the expected pattern of access token requests, allowing for the configurable window of time for the client to request the access token within and how close (i.e., within a client-defined threshold) to the expiration of the current access token the client is willing to use the current access token (e.g., the fixed lifetime of thirty seconds). In addition, the authorization server may also utilize other pieces of information corresponding to the access token request, such as, for example, the IP address of the client, to establish different instances of that client requesting access tokens. 
     If the authorization server determines that a client access token request deviates from the expected pattern of client access token request behavior, then the authorization server considers the current access token request as an invalid (e.g., illegitimate) access token request. The authorization server tags the current access token request as invalid and sends a notification to the client owner or administrator that client credentials have been compromised and to take appropriate action. The authorization server may also automatically perform one or more other action steps, such as, for example, instruct the resource server to deny access to protected resources by the client, lock the client, disable access tokens corresponding to the client, and the like. 
     Thus, illustrative embodiments can detect when client credentials have been compromised (e.g., misappropriated) and are being used by an unauthorized client to try to access a protected resource using the compromised client credentials. Illustrative embodiments detect when client credential have been compromised by enforcing a specific time interval at which a client must exchange credentials for an access token. In other words, illustrative embodiments measure the time interval between client access token requests and enforce that specific time interval. Currently, no solutions exist that can detect unauthorized protected resource access by leveraging expected patterns of client access token requests to determine when compromised client credentials are being used. 
     Therefore, illustrative embodiments provide one or more technical solutions that overcome a technical problem with detecting when compromised client credentials are being used by unauthorized users to access protected resources connected to a network. As a result, these one or more technical solutions provide a technical effect and practical application in the field of network security. 
     With reference now to  FIG. 3 , a diagram illustrating an example of client access token request validation is depicted in accordance with an illustrative embodiment. Client access token request validation process  300  may be implemented in a computer, such as, for example, the authorization server  106  in  FIG. 1  or data processing system  200  in  FIG. 2 . 
     In this example, client access token request validation process  300  includes valid client access token request  302 , valid client access token request  304 , valid client access token request  306 , valid client access token request  308 , valid client access token request  310 , and invalid client access token request  312 . However, it should be noted that client access token request validation process  300  is intended as an example only and not as a limitation on illustrative embodiments. In other words, client access token request validation process  300  may include any number of valid and invalid client access token requests. 
     A client, such as, for example, client  110  in  FIG. 1 , performs valid client access token requests  302 ,  304 ,  306 ,  308 , and  310 . In other words, the client is an authorized client. Another client, such as, for example, client  112  in  FIG. 1 , performs invalid client access token request  312 . In other words, the other client is an unauthorized client. 
     The authorization server allows valid client access token requests  302 ,  304 ,  306 ,  308 , and  310  performed by the client based on a regular time interval  314  between valid client access token request  302  and valid client access token request  304 , regular time interval  316  between valid client access token request  304  and valid client access token request  306 , and regular time interval  318  between valid client access token request  308  and valid client access token request  310 . In this example, regular time intervals  314 ,  316 ,  318  are each “N” number of seconds in length. However, it should be noted that regular time intervals  314 ,  316 ,  318  may be measured in minutes, hours, days, or the like instead of seconds. Regular time intervals  314 ,  316 ,  318  are consistent spans of time between each respective valid client access token request and may be, for example, the regular time interval  236  in  FIG. 2 . In other words, the regular time interval between access token requests performed by the authorized client is consistently repeated. As a result, the authorization server issues a new access token to the authorized client after each valid access token request based on the access token requests being performed at the regular time interval. 
     Because the other client performed invalid client access token request  312  at an irregular time interval  320  (i.e., “X” number of seconds between access token requests instead of “N” number of seconds corresponding to the regular time interval for the client), the authorization server raises an event and denies invalid client access token request  312  performed by the other client. As a result, the authorization server detects compromised credentials corresponding to the client and notifies, for example, an owner or administrator of the client regarding the compromised credentials. Further, because the other client performed invalid client access token request  312  at “X” number of seconds to produce irregular time interval  320 , the irregular time interval  322  (i.e., “X-N” number of seconds is produced between invalid client access token request  312  and valid client access token request  310 . 
     With reference now to  FIGS. 4A-4B , a flowchart illustrating a process for managing client access token requests is shown in accordance with an illustrative embodiment. The process shown in  FIGS. 4A-4B  may be implemented in a computer, such as, for example, the authorization server  106  in  FIG. 1  or data processing system  200  in  FIG. 2 . For example, the process shown in  FIGS. 4A-4B  may be implemented in access token manager  218  in  FIG. 2 . 
     The process begins when the computer receives a current access token request from a client via a network to access a protected resource hosted by a resource server connected to the network (step  402 ). In response to receiving the current access token request from the client, the computer makes a determination as to whether a regular access token request interval has been determined for the client (step  404 ). 
     If the computer determines that a regular access token request interval has not been determined for the client, no output of step  404 , then the computer allows the current access token request as a first access token request for the client (step  406 ). The computer also records a timestamp of the first access token request by the client to determine the regular access token request interval for the client in future (step  408 ). In addition, the computer generates an access token for the client to access the protected resource hosted by the resource server (step  410 ). Further, the computer issues the access token to the client via the network (step  412 ). Thereafter, the process terminates. 
     Returning to step  404 , if the computer determines that a regular access token request interval has been determined for the client, yes output of step  404 , then the computer retrieves the regular access token request time interval for the client (step  414 ). The computer also retrieves a timestamp of the last allowed access token request by the client (step  416 ). The computer compares the timestamp of the last allowed access token request by the client with a timestamp of the current access token request received from the client (step  418 ). The computer determines a current time interval between the last allowed access token request and the current access token request based on a comparison of timestamps (step  420 ). Afterward, the computer makes a determination as to whether the current time interval matches the regular access token request interval for the client within a configurable time window (step  422 ). 
     If the computer determines that the current time interval does match the regular access token request interval for the client within the configurable time window, yes output of step  422 , then the computer allows the current access token request (step  424 ). In addition, the computer records the timestamp of the current access token request as the last allowed access token request by the client in response to allowing the current access token request (step  426 ). Thereafter, the process returns to step  410 , where the computer generates an access token for the client based on allowing the current access token request. 
     Returning to step  422 , if the computer determines that the current time interval does not match the regular access token request interval for the client within the configurable time window, no output of step  422 , then the computer denies the current access token request (step  428 ) and determines that credentials corresponding to the client have been compromised. Further, the computer automatically performs a set of action steps corresponding to denial of the current access token request (step  430 ). Thereafter, the process terminates. 
     Thus, illustrative embodiments of the present disclosure provide a computer-implemented method, computer system, and computer program product for detecting compromised client credentials to prevent unauthorized access to protected resources hosted by resource servers connected to a network. The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.