Patent Document

RELATED APPLICATION 
     This Application is a continuation (and claims the benefit of priority under 35 U.S.C. §120) of U.S. application Ser. No. 12/068,834, filed Feb. 12, 2008, entitled “BOOTSTRAP OS PROTECTION AND RECOVERY,” Inventors Akos Horvath, et al., the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to detecting a kernel-mode rootkit that hooks the Windows System Service Dispatch Table. 
     2. Description of the Related Art 
     A rootkit is a set of software tools intended to conceal running processes, files or system data, thereby helping an intruder to maintain access to a system whilst avoiding detection. Rootkits are known to exist for a variety of operating systems such as Linux, Solaris and versions of Microsoft Windows. Rootkits often modify parts of the operating system or install themselves as drivers or kernel modules. Rootkits need to hide something, whether it is a process, a thread, a file, or a registry entry, etc. from user mode applications and from kernel mode device drivers. To achieve that, Rootkits have to alter the execution path of the file system, the processes, the threads and the registry functions. 
     One popular technique used by Rootkits device drivers is to hook the file system, the process, and the registry query functions inside the System Service Dispatch Table (SSDT) by replacing the functions pointers inside the SSDT table with new pointers that point to their own functions. This change of the execution path would affect all Nt/Zw function calls made by user mode applications and all Zw function calls made by kernel mode device drivers. 
     A number of techniques for detecting rootkits and protecting computer systems from rootkits have arisen. However, as implemented, these techniques only start protecting the computer system after the operating system has been loaded. Rootkits, or other bad software (malware) can run before the detection and protection software is loaded to memory and allowed to execute. This may cause a problem in that the detection and protection software may miss the presence of the rootkit or to be affected or modified by the rootkit. 
     Another problem arises when detection and protection software malfunctions (such as due to a bug in the software) and blocks the ability of the computer system to access the Internet. Typically, such malfunctions are corrected by downloading an update or patch to the software over the Internet. However, if the malfunction itself prevents the computer system from accessing the Internet, it becomes very difficult for the typical update mechanism to download an update or patch that will resolve the bug causing the failure to access the Internet. Such a bug would also prevent the user of the computer system from manually getting an update website to download a patch to resolve the issue. 
     A need arises for a technique by which malware detection and protection software can detect malware, such as rootkits, before the operating system has been loaded and which provides the capability to patch malfunctions that block the ability of the computer system to access the Internet. 
     SUMMARY OF THE INVENTION 
     A method, system, and computer program product for protecting a computer system provides bootstrap operating system detection and recovery and provides the capability to detect malware, such as rootkits, before the operating system has been loaded and provides the capability to patch malfunctions that block the ability of the computer system to access the Internet. 
     A method for protecting a computer system comprises the steps of reading stored status information indicating whether network connectivity was available the last time an operating system of the computer system was operational, when the stored status information indicates that network connectivity was not available, obtaining a software patch, and executing and applying the software patch. These steps are performed after only a portion of a boot process has been performed and before the operating system of the computer system is operational. The portion of a boot process that has been performed is the power-on self-test. 
     The step of obtaining the software patch comprises the steps of loading a stand-alone network driver, using the stand-alone network driver to connect to a device on a network, and downloading the software patch from the device on the network. 
     The method further comprises the steps of scanning files needed to complete the boot process to determine integrity of the files and if the integrity of the files is intact, completing the boot process. If the integrity of the files is not intact, corrective action is taken. The corrective action comprises halting the boot process, or restoring the files and completing the boot process. 
     The method further comprises the steps of upon completion of the boot process, determining whether network connectivity is available and storing status information indicating whether network connectivity is available. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The details of the present invention, both as to its structure and operation, can best be understood by referring to the accompanying drawings, in which like reference numbers and designations refer to like elements. 
         FIG. 1  is an exemplary block diagram of a computer system  100  in which the present invention may be implemented. 
         FIG. 2  is an exemplary flow diagram of a process, which is performed by the security software shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An exemplary block diagram of a computer system  100  in which the present invention may be implemented is shown in  FIG. 1 . Computer system  100  is typically a programmed general-purpose computer system, such as a personal computer, workstation, server system, and minicomputer or mainframe computer. Computer system  100  includes processor (CPU)  102 , input/output circuitry  104 , network adapter  106 , memory  108 , and mass storage  110 . CPU  102  executes program instructions in order to carry out the functions of the present invention. Typically, CPU  102  is a microprocessor, such as an INTEL PENTIUM® processor, but may also be a minicomputer or mainframe computer processor. Although in the example shown in  FIG. 1 , computer system  100  is a single processor computer system, the present invention contemplates implementation on a system or systems that provide multi-processor, multi-tasking, multi-process, multi-thread computing, distributed computing, and/or networked computing, as well as implementation on systems that provide only single processor, single thread computing. Likewise, the present invention also contemplates embodiments that utilize a distributed implementation, in which computer system  100  is implemented on a plurality of networked computer systems, which may be single-processor computer systems, multi-processor computer systems, or a mix thereof. 
     Input/output circuitry  104  provides the capability to input data to, or output data from, computer system  100 . For example, input/output circuitry may include input devices, such as keyboards, mice, touchpads, trackballs, scanners, etc., output devices, such as video adapters, monitors, printers, etc., and input/output devices, such as, modems, etc. Network adapter  106  interfaces computer system  100  with network  111 . Network  111  may be any standard local area network (LAN) or wide area network (WAN), such as Ethernet, Token Ring, the Internet, or a private or proprietary LAN/WAN. 
     Memory  108  stores program instructions that are executed by, and data that are used and processed by, CPU  102  to perform the functions of the present invention. Memory  108  may include volatile memory  112 , including electronic memory devices such as random-access memory (RAM), and non-volatile memory  114 , including electronic memory devices such as read-only memory (ROM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), flash memory, etc. Mass storage  110  provides the capability to store large amounts of information, such as program instructions and data, in a persistent and accessible form. Mass storage  110  typically includes electro-mechanical storage devices, such as magnetic disk drives, tape drives, optical disk drives, etc., which may use an integrated drive electronics (IDE) interface, or a variation or enhancement thereof, such as enhanced IDE (EIDE) ultra direct memory access (UDMA), or Serial Advanced Technology Attachment (SATA), or a small computer system interface (SCSI) based interface, or a variation or enhancement thereof, such as fast-SCSI, wide-SCSI, fast and wide-SCSI, etc, or a fiber channel-arbitrated loop (FC-AL), etc. Mass storage  110  may also include electronic memory devices, which are typically non-volatile devices, such as those described above, but which also may be volatile memory devices. 
     In a typical modern computer system, non-volatile memory  114  includes a Basic Input/Output System  116  (BIOS), which includes program code that performs a number of important functions, including booting the computer. Booting, also known as booting up or bootstrapping, is a process that performs the operations required to place a computer into its normal operating configuration after power is supplied to the hardware, or after a reset is performed. Most computer systems can only execute code stored in memory devices, such as ROM or RAM. Modern operating systems are stored on hard disks, or other non-volatile mass storage devices. When a computer is first powered on, it doesn&#39;t have an operating system stored in its memory devices. A special program, called a bootstrap loader, bootstrap or boot loader is used to load the software needed for the operating system to start. Often, multiple-stage boot loaders are used, in which several small programs of increasing complexity load each other, until the last of them loads the operating system. 
     Typically, the first function after power-on that is performed by a BIOS is the Power-On Self-Test  118  (POST). A typical BIOS will perform at least some of the following functions during POST, although not necessarily in the listed order:
         verify the functionality of the process (CPU);   verify the integrity of the BIOS code itself;   determine the reason POST is being executed (cold or warm restart, exit from power saving mode, etc.);   find, size, and verify system main memory;   discover, initialize, and catalog all system buses and devices;   pass control to other specialized BIOSes or bootloader programs;   provide a user interface for system&#39;s configuration;   identify, organize, and select which devices are available for booting; and   construct whatever system environment that is required by the target OS.       

     In the present invention, BIOS  116  passes control to a specialized security software, which performs the functions of the present invention. Preferably, control is passed to security software immediately after completion of the POST operations of verifying the functionality of the process (CPU), verifying the integrity of the BIOS code, determining the reason POST is being executed, verifying system main memory, and initializing system buses and devices. 
     An exemplary flow diagram of a process  200 , which is performed by the security software, is shown in  FIG. 2 . It is best viewed in conjunction with  FIG. 1 . Process  200  begins with step  202 , in which a stored status  122  is read. Security software  120  reads status  122  to determine whether network connectivity was correctly functioning the last time the operating system of the computer system was operational. This status  122  is stored in step  212  below and may be stored in one or more of a variety of secure locations, such as in non-volatile memory  114 , mass storage  110 , or on a network device  126  that is communicatively connected to computer system  100  by network  111 . Security software  120  and the location in which status  122  is stored may be checked to determine whether tampering has occurred, for example, by determining a checksum or hash of the memory or files in which security software and/or status  122  are stored. Such a checksum or hash may be stored in non-volatile memory (not shown), as in BIOS  116  or elsewhere, in mass storage  110  (not shown), or on a network device (not shown) on network  111 . 
     In step  204 , if the status is bad, this indicates no network connectivity that no network connectivity was available the last time the operating system of the computer system was operational. Typically, network connectivity will not be available due to a bug in software that is loaded during start up of the operating system, such as anti-malware software. When the status is bad, security software  120  loads its own stand-alone (not involving the operating system) network driver software  124  and makes a direct network connection over network  111  to a network device (not shown) from which a software patch may be downloaded. For example, security software  120  may connect to a particular website and download a software patch. Depending upon the nature of the patch, the patch may be executed and applied at this time, or the patch may be executed and applied after the operating system is operational (see step  214 ). 
     In step  206 , security software  120  performs an integrity and/or malware scan of critical software, such as BIOS  116 , critical operating system files, such as the portion of the standard bootloader  126  that is stored in mass storage  110 , and anti-malware software  122 . If anomalies or malware are detected by this scan, security software  120  takes appropriate corrective action, such as restoring critical files from a secure location on mass storage  110  or from a network device (not shown) on network  111 . Alternatively, the boot process can be halted, in which case manual repair is necessary. 
     In step  208 , security software  120  loads the operating system standard bootloader  126  and executes it, allowing the operating system to continue its booting operation from the point at which the POST operation passed control to security software  120 . 
     In step  210 , the operating system boots normally. In step  212 , anti-malware software  122 , which is loaded automatically when the operating system boots normally, performs a diagnostic scan to ensure that network connectivity is available and its update mechanism is functioning. Anti-malware software  122  stores the result of this diagnostic scan as a status  122  that is examined by security software  120  in step  204  the next time the computer is booted. In step  214 , if a patch was downloaded in step  204  and the nature of the patch is such that is to be executed once the operating system is operational, that patch is executed in order to update the corresponding software. 
     In one possible implementation, security software  120 A can be stored as a bootloader program itself on mass storage  110 , such as a hard disk drive. In this implementation, the first sector of the hard disk drive is altered to load security software  120 A upon the POST process passing control to the software in the first sector of the hard drive. As there are other special bootloader programs that may be installed in a computer system, such as special bootloaders that provide a user with a choice of operating system to load, security software  120 A should be aware of the other special bootloader programs. In particular, security software  120 A should ensure that it runs before any other special bootloader programs run, and that, upon successful completion of security software  120 A, control is passed to the correct special bootloader program. While this is easily achieved if security software  120 A is installed after any other special bootloader programs, additional steps must be taken if another special bootloader program is installed after security software  120 A is installed. In this case, the other special bootloader program may overwrite the first sector of the hard disk drive. Security software  120 A or anti-malware software  122  must therefore subsequently detect that the first sector of the hard disk drive has been overwritten and restore the first sector of the hard disk drive so that security software  120 A runs properly. This is also useful in the case where the first sector of the hard disk drive has been overwritten or modified due to malware or error. 
     Although specific embodiments of the present invention have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims.

Technology Category: 5