Chapter 12 - Security_b43a9c06273a93e1bd4f480d4ebca309.pdf

Computer Security: Principles and Practice Fifth Edition Chapter 12 Operating System Security Copyright © 2024, 2018, 2015 Pearson Education, Inc. All Rights Reserved Operating System Security Layers Figure...

Computer Security: Principles and Practice Fifth Edition Chapter 12 Operating System Security Copyright © 2024, 2018, 2015 Pearson Education, Inc. All Rights Reserved Operating System Security Layers Figure 12.1 Strategies (1 of 2) The 2010 Australian Signals Directorate (ASD) lists the “Strategies to Mitigate Cyber Security Incidents” At least 85% of the targeted cyber intrusions investigated by ASD would have been prevented The four strategies for prevention are: Allow-list approved applications Patch third-party applications and operating system vulnerabilities Restrict administrative privileges Strategies (2 of 2) Configure Microsoft In 2017, the updated Office macro settings list “Essential Eight” was published User application hardening It adds the following items: Multifactor authentication Collectively these assist in creating a defense-in-depth Regular backups system Operating System Security Possible for a system to be compromised during the installation process before it can install the latest patches Building and deploying a system should be a planned process designed to counter this threat Process must: Assess risks and plan the system deployment Secure the underlying operating system and then the key applications Ensure any critical content is secured Ensure appropriate network protection mechanisms are used Ensure appropriate processes are used to maintain security  System Security Planning The first step in deploying a new system is planning Plan needs to identify appropriate Planning should include personnel and a wide security training to install and assessment of the manage the system organization Aim is to maximize Planning process needs security while to determine security minimizing costs requirements for the system, applications, data, and users  System Security Planning Process The purpose of the system, the type of information stored, the applications and services provided, and their security requirements The categories of users of the system, the privileges they have, and the types of information they can access How the users are authenticated How access to the information stored on the system is managed What access the system has to information stored on other hosts, such as file or database servers, and how this is managed Who will administer the system and how they will manage the system (via local or remote access)  Operating Systems Hardening First critical step in securing Basic steps a system is to secure the Install and patch the operating system base operating system Harden and configure the operating system to adequately address the identified security needs of the system by: Removing unnecessary services, applications, and protocols Install and configure additional security controls, such as anti-virus, host-based firewalls, and intrusion detection system (I D S) Test the security of the basic operating system to ensure that the steps taken adequately address its security needs Initial Setup and Patching System security begins with the installation of the operating system Ideally, new systems should be constructed on a protected network Full installation and hardening process should occur before the system is deployed to its intended location Initial installation should install the minimum necessary for the desired system Overall boot process must also be secured The integrity and source of any additional device driver code must be carefully validated Critical that a system be kept up to date, with all critical security related patches installed Should stage and validate all patches on test systems before deploying them in production Remove Unnecessary Services, Applications, and Protocols If fewer software packages are available to run, the risk is reduced System planning process should identify what is actually required for a given system When performing the initial installation the supplied defaults should not be used Default configuration is set to maximize ease of use and functionality rather than security If additional packages are needed later they can be installed when they are required Configure Users, Groups, and Authentication Not all users with access to a system will have the same access to all data and resources on that system Elevated privileges should be restricted to only those users who require them, and then only when they are needed to perform a task Categories of users on the system System planning process should Privileges they have consider: Types of information they can access How and where they are defined and authenticated Those which are not required should be either removed or Default accounts included as part of the disabled system installation should be secured Policies that apply to authentication credentials configured  Configure Resource Controls and Install Additional Security Controls Further security possible by installing Once the users and groups are and configuring additional security defined, appropriate permissions tools: can be set on data and resources Anti-virus software Many of the security hardening guides Host-based firewalls provide lists of recommended IDS or IPS software changes to the default access Allow-list applications configuration Test the System Security Final step in the process of initially securing the base operating system is security testing Goal: Ensure the previous security configuration steps are correctly implemented Identify any possible vulnerabilities Checklists are included in security hardening guides There are programs specifically designed to: Review a system to ensure that it meets the basic security requirements Scan for known vulnerabilities and poor configuration practices Should be done following the initial hardening of the system Repeated periodically as part of the security maintenance process Application Configuration Creating and specifying appropriate data storage areas for application May include: Making appropriate changes to the application or service default configuration details Default data Some applications or services may Scripts include: User accounts Of particular concern with remotely Risk from this form of attack is reduced accessed services such as Web and by ensuring that most of the files can be file transfer services read, but not written, by the server Encryption Technology Is a key enabling technology that may be used to secure data both in transit and when stored Must be configured and appropriate cryptographic keys created, signed, and secured If secure network services are provided using TLS or IP sec suitable public and private keys must be generated for each of them If secure network services are provided using SSH, an appropriate server and client keys must be created Cryptographic file systems are another use of encryption Security Maintenance Process of maintaining security is continuous Security maintenance includes: Monitoring and analyzing logging information Performing regular backups Recovering from security compromises Regularly testing system security Using appropriate software maintenance processes to patch and update all critical software and to monitor and revise configuration as needed Logging In the event of a system Key is to ensure that you Can only inform you breach or failure, system capture the correct data about bad things that administrators can more and then appropriately have already happened quickly identify what monitor and analyze happened these data Generates significant Information can be Range of data acquired volumes of information generated by the should be determined and it is important that system, network and during the system sufficient space is applications planning stage allocated for it Automated analysis is preferred Data Backup and Archive (1 of 2) Performing regular backups of data is a critical control that assists with maintaining the integrity of the system and user data May be legal or operational requirements for the retention of data Backup The process of making copies of data at regular intervals Archive The process of retaining copies of data over extended periods of time in order to meet legal and operational requirements to access past data Data Backup and Archive (2 of 2) Needs and policy relating to backup and archive should be determined during the system planning stage Kept online or offline Stored locally or transported to a remote site Trade-offs include ease of implementation and cost versus greater security and robustness against different threats Linux/Unix Security (2 of 4) Users, groups, and permissions Access is specified as granting read, write, and execute permissions to each of owner, group, and others for each resource Guides recommend changing the access permissions for critical directories and files Local exploit Software vulnerability that can be exploited by an attacker to gain elevated privileges Remote exploit Software vulnerability in a network server that could be triggered by a remote attacker Linux/Unix Security (4 of 4) chroot jail Restricts the server’s view of the file system to just a specified portion Uses chroot system call to confine a process by mapping the root of the filesystem to some other directory File directories outside the chroot jail aren’t visible or reachable Main disadvantage is added complexity  Windows Security (1 of 3) Users administration and Patch management access controls “Windows Update” and Systems implement “Windows Server Update discretionary access controls Service” assist with regular resources maintenance and should be Vista and later systems include used mandatory integrity controls Third party applications also Objects are labeled as being of provide automatic update low, medium, high, or system support integrity level System ensures the subject’s integrity is equal to or higher than the object’s level Implements a form of the Biba Integrity model Windows Security: Users Administration and Access Controls Windows Combination of share and N T F User Low systems S permissions Account Privilege also define may be used to privileges provide additional Control Service security and (U A C) Accounts granularity when accessing files on a shared resource Provided in Vista and Used for long- System later systems lived service wide and Assists with ensuring processes such granted to users with as file, print, user administrative rights and D N S accounts only use them when services required, otherwise access the system as normal users Windows Security (2 of 3) Application and service configuration Much of the configuration information is centralized in the Registry Forms a database of keys and values that may be queried and interpreted by applications Registry keys can be directly modified using the “Registry Editor” More useful for making bulk changes  Windows Security (3 of 3) Other security controls Windows systems also support a range of cryptographic functions: Essential that anti-virus, anti-spyware, Encrypting files and directories using the personal firewall, and other malware and Encrypting File System (E F S) attack detection and handling software Full-disk encryption with A E S using BitLocker packages are installed and configured Current generation Windows systems include basic firewall and malware countermeasure capabilities Important to ensure the set of products in use are compatible Virtualization A technology that provides Provides support for an abstraction of the Benefits include multiple distinct Raises resources used by some software which runs in a better efficiency in operating systems and additional simulated environment the use of the physical associated security called a virtual machine (V system resources applications on one M) physical system concerns Hypervisor Software that sits between the hardware and the VMs Acts as a resource broker It allows multiple VMs to safely coexist on a single physical server host and share that host’s resources Virtualizing software provides abstraction of all physical resources and thus enables multiple computing stacks, called virtual machines, to be run on a single physical host Each VM includes an OS, called the guest OS This OS may be the same as the host OS, if present, or a different one Hypervisor Functions The principal functions performed by a hypervisor are: Execution management of VMs Devices emulation and access control Execution of privileged operations by hypervisor for guest VMs Management of VMs (also called VM lifecycle management) Administration of hypervisor platform and hypervisor software Comparison of Virtual Machines and Containers Figure 12.2 Virtualized Systems In virtualized systems, the available hardware resources must be appropriately shared among the various guest OSs These include CPU, memory, disk, network, and other attached devices CPU and memory are generally partitioned between these, and scheduled as required Disk storage may be partitioned, with each guest having exclusive use of some disk resources Alternatively, a “virtual disk” may be created for each guest, which appears to it as a physical disk with a full file-system but is viewed externally as a single ”disk image” file on the underlying file-system Attached devices such as optical disks or USB devices are generally allocated to a single guest OS at a time Containers In this approach, software A recent approach to known as a virtualization virtualization is known as container, runs on top of the container virtualization or host O S kernel and provides application virtualization an isolated execution environment for applications Unlike hypervisor-based V M s, All containerized applications containers do not aim to emulate on a host share a common O physical servers S kernel Containerization sits between For containers, only a small the O S and applications and container engine is required incurs lower overhead but as support potentially introduces greater security vulnerabilities Virtualization Security Issues Security concerns include: Guest OS isolation Ensuring that programs executing within a guest OS may access and use only the resources allocated to it Guest OS monitoring by the hypervisor Which has privileged access to the programs and data in each guest OS Virtualized environment security Particularly image and snapshot management which attackers may attempt to view or modify Securing Virtualization Systems Organizations using virtualization should: Carefully plan the security of the virtualized system Secure all elements of a full virtualization solution and maintain their security Ensure that the hypervisor is properly secured Restrict and protect administrator access to the virtualization solution Hypervisor Security Should be Secured using a process similar to securing an operating system Installed in an isolated environment Configured so that it is updated automatically Monitored for any signs of compromise Accessed only by authorized administration May support both local and remote administration so must be configured appropriately Remote administration access should be considered and secured in the design of any network firewall and IDS capability in use Ideally administration traffic should use a separate network with very limited access provided from outside the organization Virtualized Infrastructure Security Systems manage access to hardware resources Access must be limited to just the appropriate guest OS s Access to VM image and snapshots must be carefully controlled  Virtual Firewall Provides firewall capabilities for the network traffic flowing between systems hosted in a virtualized or cloud environment that does not require this traffic to be routed out to a physically separate network supporting traditional firewall services VM Bastion Host Where a separate VM is used as a bastion host supporting the same firewall systems and services that could be configured to run on a physically separate bastion, including possibly IDS and IPS services VM Host-Based Firewall Where host-based firewall capabilities provided by the guest OS running on the VM are configured to secure that host in the same manner as used in physically separate systems Hypervisor Firewall Where firewall capabilities are provided directly by the hypervisor Hosted Virtualization Security Hosted virtualized systems pose additional security concerns that result from the host O S under the hypervisor and its guest Oss Users have access to configure the hypervisor and to any V M images and snapshots Possible to design a host system and virtualization solution that is more protected from access and modification by the users There will be security concerns from possible compromise unless it is adequately secured and managed Figure 12.3 Reference Monitor Concept Trusted Platform Module (1 of 4) A concept being standardized by the Trusted Computing Group A hardware module that is used in hardware/software approach to trusted computing Trusted computing (T C) approach employs a T P M chip on a computer Generates keys that is shared with vulnerable components Trusted Platform Module (2 of 4) Authenticated Boot Service Boots the entire operating system in stages Assures that each portion of the OS is an approved version A tamper-evident log of the loading process is kept to detect tampering The tamper-resistant log contains a record that establishes which version of the OS is running. Trusted Platform Module (3 of 4) Certification Service The TPM produces a digital certificate by signing a formatted description of the configuration information using the TPM’s private key. Another user can have confidence because The TPM is considered trustworthy Only the TPM possesses this TPM’s private key Trusted Platform Module (4 of 4) Encryption Service Enables data encryption in such a way that the data can be decrypted only by a certain machine TPM maintains a master secret key unique to this machine and generates a secret encryption key for every possible configuration of that machine This scheme can be extended upward Figure 12.4 TPM Component Architecture Summary (1 of 4) Introduction to operating system security System security planning Operating systems hardening Operating system installation: initial setup and patching Remove unnecessary services, applications and protocols Configure users, groups, and authentications Configure resource controls Install additional security controls Test the system security Application security Application configuration Encryption technology Summary (2 of 4) Security maintenance Logging Data backup and archive Linux/Unix security Patch management Application and service configuration Users, groups, and permissions Remote access controls Logging and log rotation Application security using a chroot jail Security testing Summary (3 of 4) Windows security Patch management Users administration and access controls Application and service configuration Other security controls Security testing Virtualization security Virtualization alternatives Virtualization security issues Securing virtualization systems Virtualized infrastructure security Virtual firewall Summary (4 of 4) Trusted computer systems Reference monitors TCSEC and common criteria Trusted platform module Authenticated boot service Certification service Encryption service TPM functions Protected storage