Semiconductor Lasers I (eBook)

Fundamentals

Eli Kapon (Autor)

eBook Download: PDF

1999 | 1. Auflage
453 Seiten
Elsevier Science (Verlag)
978-0-08-054092-4 (ISBN)

Infos

This book covers the device physics of semiconductor lasers in five chapters written by recognized experts in this field. The volume begins by introducing the basic mechanisms of optical gain in semiconductors and the role of quantum confinement in modern quantum well diode lasers. Subsequent chapters treat the effects of built-in strain, one of the important recent advances in the technology of these lasers, and the physical mechanisms underlying the dynamics and high speed modulation of these devices. The book concludes with chapters addressing the control of photon states in squeezed-light and microcavity structures, and electron states in low dimensional quantum wire and quantum dot lasers.
The book offers useful information for both readers unfamiliar with semiconductor lasers, through the introductory parts of each chapter, as well as a state-of-the-art discussion of some of the most advanced semiconductor laser structures, intended for readers engaged in research in this field. This book may also serve as an introduction for the companion volume, Semiconductor Lasers II: Materials and Structures, which presents further details on the different material systems and laser structures used for achieving specific diode laser performance features.


* Introduces the reader to the basics of semiconductor lasers
* Covers the fundamentals of lasing in semiconductors, including quantum confined and microcavity structures
* Beneficial to readers interested in the more general aspects of semiconductor physics and optoelectronic devices, such as quantum confined heterostructures and integrated optics
* Each chapter contains a thorough introduction to the topic geared toward the non-expert, followed by an in-depth discussion of current technology and future trends
* Useful for professionals engaged in research and development
* Contains numerous schematic and data-containing illustrations

Inhalt

Fornt Cover 1
Nessus Network Auditing, Second Edition 2
Copyright Page 3
Technical Editor 4
Contributing Authors 5
Contents 8
Chapter 1: Vulnerability Assessment 16
Introduction 17
What Is a Vulnerability Assessment? 17
Why a Vulnerability Assessment? 18
Assessment Types 20
Host Assessments 20
Network Assessments 21
Automated Assessments 22
Stand-Alone vs. Subscription 22
The Assessment Process 23
Detecting Live Systems 24
Identifying Live Systems 24
Enumerating Services 24
Identifying Services 26
Identifying Applications 26
Identifying Vulnerabilities 27
Reporting Vulnerabilities 27
Two Approaches 28
Administrative Approach 29
The Outsider Approach 30
The Hybrid Approach 30
Realistic Expectations 32
Summary 36
Solutions Fast Track 37
Frequently Asked Questions 38
Chapter 2: Introducing Nessus 40
Introduction 41
What Is It? 41
The De Facto Standard 42
History 44
Basic Components 46
Client and Server 46
The Plugins 49
The Knowledge Base 50
Summary 51
Solutions Fast Track 51
Frequently Asked Questions 53
Chapter 3: Installing Nessus 54
Introduction 55
Nessus Version Comparison 55
Picking a Server 56
Supported Operating Systems 57
Minimal Hardware Specifications 58
Network Location 59
Nessus 2.2.x Install Guide 60
Nessus Install Script 60
Installation from Source 64
./configure 64
Nessus 3 Install Guide 68
Mac OS X Install Process 68
UNIX Install Process 72
Fresh Installation 72
Red Hat and SUSE 72
Debian 73
Solaris 73
FreeBSD 73
Upgrading from Nessus 2 73
Configuring Nessus for UNIX 74
Creating a User Account 76
Windows Install Process 79
Final Steps 82
Installing a Client 89
Summary 91
Solutions Fast Track 91
Frequently Asked Questions 93
Chapter 4: Running Your First Scan 94
Introduction 95
Preparing for Your First Scan 95
Authorization 95
Risk vs. Benefit 96
Denial of Service 96
Missing Information 97
Providing Authentication Information 97
Plugin Selection 98
Starting the Nessus Client 98
Policies 102
Policy Tab 104
Options Tab 104
Credentials Tab 109
Plugin Selection Tab 112
Network Tab 116
Advanced Tab 118
Target Selection 130
Starting the Scan 134
Nessus Command Line 137
Summary 139
Solutions Fast Track 139
Frequently Asked Questions 142
Chapter 5: Interpreting Results 144
Introduction 145
The Nessus UI Basics 145
Viewing Results Using the Nessus 3 Client for Linux/UNIX and Windows 145
Using the Basic Report Viewer 146
Saving and Exporting to Other Formats 147
Loading and Importing Reports 151
Reading a Nessus Report 153
Understanding Vulnerabilities 153
Understanding Risk 154
Understanding Scanner Logic 156
Key Report Elements 159
Asking the Right Questions 165
Factors that Can Affect Scanner Output 169
Plugin Selection 169
The Role of Dependencies 170
Safe Checks 170
no404.nasl 171
Ping the Remote Host 172
Portscanner Settings 172
Proxies, Firewalls, and TCP Wrappers 172
Valid Credentials 173
KB Reuse and Differential Scanning 173
And Many More... 173
Scanning Web Servers and Web Sites 174
Web Servers and Load Balancing 174
Bugs in the Plugins 175
Additional Reading 176
Configuration Files 176
NASL 178
The Nessus KB 178
The Nessus Logs 178
Forums and Mailing Lists 179
Summary 180
Solutions Fast Track 180
Frequently Asked Questions 182
Chapter 6: Vulnerability Types 184
Introduction 185
Critical Vulnerabilities 185
Buffer Overflows 187
Directory Traversal 188
Format String Attacks 189
Default Passwords 190
Misconfigurations 191
Known Backdoors 191
Information Leaks 192
Memory Disclosure 193
Network Information 194
Version Information 194
Path Disclosure 195
User Enumeration 196
Denial of Service 196
Best Practices 198
Summary 200
Solutions Fast Track 200
Frequently Asked Questions 202
Chapter 7: False Positives 204
Introduction 205
What Are False Positives? 205
A Working Definition of False Positives 205
Why False Positives Matter 208
False Positives Waste Your Time 208
False Positives Waste Others' Time 208
False Positives Cost Credibility 209
Generic Approaches to Testing 209
An Overview of Intrusive Scanning 209
An Overview of Nonintrusive Scanning 210
The Nessus Approach to Testing 211
Dealing with False Positives 213
Dealing with Noise 214
Analyzing the Report 215
False Positives, and Your Part in Their Downfall 218
Dealing with a False Positive 218
Disabling a Nessus Plugin 219
Disabling a Plugin with Nessus 3 219
Disabling a Plugin Under Unix 223
Marking a Result as a False Positive with NessusWX 226
False Positives and Web Servers-Dealing with Friendly 404s 228
Summary 231
Solutions Fast Track 231
Frequently Asked Questions 232
Chapter 8: Under the Hood 234
Introduction 235
Nessus Architecture and Design 236
Host Detection 239
Service Detection 243
Information Gathering 246
Vulnerability Fingerprinting 249
Denial-of-Service Testing 251
Putting It All Together 253
Summary 259
Solutions Fast Track 259
Frequently Asked Questions 261
Chapter 9: The Nessus Knowledge Base 262
Introduction 263
Knowledge Base Basics 263
What Is the Knowledge Base? 263
A word about the "Policy.xml" file 264
Where the Knowledge Base Is Stored 265
Using the Knowledge Base 266
Information Exchange 274
How Plugins Use the Knowledge Base to Share Data 274
The Type of Data that Is Stored 282
Dependency Trees 283
Limitations 283
Using get_kb_item and fork 283
Summary 287
Solutions Fast Track 287
Frequently Asked Questions 289
Chapter 10: Enterprise Scanning 290
Introduction 291
Planning a Deployment 291
Define Your Needs 291
Planning 291
Preparation 294
Segmentation 295
Network Topology 296
Bandwidth Requirements 298
Portscanning Phase 299
Testing Phase 301
Automating the Procedure 303
Configuring Scanners 306
Assigning the Tasks 306
System Requirements 308
Scanning for a Specific Threat 311
Best Practices 313
Divide and Conquer 313
Segregate and Limit 313
Certificates for the Forgetful 314
Speed Is Not Your Enemy 314
Keep a Watchful Eye 315
Data Correlation 315
Combining Reports 315
Preparing Your Database 315
Differential Reporting 322
Filtering Reports 331
Third-Party Tools 333
Extracting Information from a Saved Session Prior to Version 2.2.0 of Nessusd Using sd2nbe 333
Nessus Integration with Perl and Net::Nessus::ScanLite Prior to Version 3.0.0 333
Nessus NBE Report Parsing Using Parse::Nessus::NBE 335
Common Problems 335
Aggressive Scanning 335
Volatile Applications 336
Printer Problems 338
Scanning Workstations 339
Summary 341
Solutions Fast Track 341
Frequently Asked Questions 343
Chapter 11: NASL 346
Introduction 347
Why NASL? 347
Why Do You Want to Write (and Publish) Your Own NASL Scripts? 350
Structure of a NASL Script 350
The Description Section 351
An Introduction to the NASL Language 355
Writing Your First Script 356
Assuming that the FTP Server Is Listening on Port 21 362
Establishing a Connection to the Port Directly 363
Respecting the FTP Protocol 363
Wrapping It Up 364
More Advanced Scripting 365
String Manipulation 365
How Strings Are Defined in NASL 365
String Addition and Subtraction 366
String Search and Replace 366
Regular Expressions in NASL 366
The NASL Protocol APIs 368
HTTP 368
FTP 370
NFS 370
Other Protocol API Libraries 372
The Nessus Knowledge Base 376
Summary 377
Solutions Fast Track 377
Frequently Asked Questions 379
Chapter 12: The Nessus User Community 380
Introduction 381
The Nessus Mailing Lists 382
Subscribing to a Mailing List 383
Sending a Message to a Mailing List 386
Accessing a List's Archives 387
The Online Plug-In Database 389
Staying Abreast of New Plug-Ins 391
Reporting Bugs via Bugzilla 391
Querying Existing Bug Reports 391
Creating and Logging In to a Bugzilla Account 394
Submitting a Bug Report 396
Submitting Patches and Plug-Ins 399
Submitting Patches 399
Submitting Plug-Ins 399
Where to Get More Information and Help 400
Summary 401
Solutions Fast Track 401
Frequently Asked Questions 403
Chapter 13: Compliance Monitoring with Nessus 3 406
Introduction 407
Understanding Compliance 407
HIPAA 408
Payment Card Industry (PCI) 408
FERPA 408
NERC 409
ISO/IEC 27002:2005 409
NIST 800 Series 409
The Nessus Compliance Engine 409
Compliance with Nessus 410
Types of audits 410
.audit Files 411
How .audit Files Work 413
Examples 413
Using Nessus 3 Auditing 417
Updating Nessus 3 Plugins 417
Creating a New Policy 419
Starting Your Audit 429
Nessus 3 Reporting 431
Summary 437
Solutions Fast Track 437
Frequently Asked Questions 439
Index 440

Textauszug

Chapter 1

Vulnerability Assessment

Solutions in this chapter:

■ What Is a Vulnerability Assessment?

■ Automated Assessments

■ Two Approaches

■ Realistic Expectations

☑ Summary

☑ Solutions Fast Track

☑ Frequently Asked Questions

Introduction

In the war zone that is the modern Internet, manually reviewing each networked system for security flaws is no longer feasible. Operating systems, applications, and network protocols have grown so complex over the last decade that it takes a dedicated security administrator to keep even a relatively small network shielded from attack.

Each technical advance brings new security holes. A new protocol might result in dozens of actual implementations, each of which could contain exploitable programming errors. Logic errors, vendor-installed backdoors, and default configurations plague everything from modern operating systems to the simplest print server. Yesterday’s viruses seem positively tame compared to the highly optimized Internet worms that continuously assault every system attached to the global Internet.

To combat these attacks, a network administrator needs the appropriate tools and knowledge to identify vulnerable systems and resolve their security problems before they can be exploited. One of the most powerful tools available today is the vulnerability assessment, and this chapter describes what it is, what it can provide you, and why you should be performing them as often as possible. Following this is an analysis of the different types of solutions available, the advantages of each, and the actual steps used by most tools during the assessment process. The next section describes two distinct approaches used by the current set of assessment tools and how choosing the right tool can make a significant impact on the security of your network. Finally, the chapter closes with the issues and limitations that you can expect when using any of the available assessment tools.

What Is a Vulnerability Assessment?

To explain vulnerability assessments, we first need to define a vulnerability. For the purposes of this book, a vulnerability refers to any programming error or misconfiguration that could allow an intruder to gain unauthorized access. This includes anything from a weak password on a router to an unpatched programming flaw in an exposed network service. Vulnerabilities are no longer the realm of just system crackers and security consultants; they have become the enabling factor behind most network worms, spyware applications, and e-mail viruses.

Spammers are increasingly relying on software vulnerabilities to hide their tracks; the open mail relays of the 1990s have been replaced by compromised “zombie” proxies of today, called botnets, created through the mass exploitation of common vulnerabilities. A question often asked is, “Why would someone target my system?” The answer is that most exploited systems were not targeted; they were simply one more address in a network range being scanned by an attacker. Spammers do not care whether a system belongs to an international bank or your grandmother Edna; as long as they can install their relay software, it makes no difference to them.

Vulnerability assessments are simply the process of locating and reporting vulnerabilities. They provide you with a way to detect and resolve security problems before someone or something can exploit them. One of the most common uses for vulnerability assessments is their capability to validate security measures. If you recently installed a new firewall or intrusion detection system (IDS), a vulnerability assessment allows you to determine how well that solution works. If your assessment completes and the IDS didn’t fire off a single alert, it might be time to have a chat with the vendor.

The actual process for vulnerability identification varies widely between solutions; however, they all focus on a single output—the report. This report provides a snapshot of all the identified vulnerabilities on the network at a given time. Components of this report usually include a list of each identified vulnerability, where it was found, what the potential risk is, and how it can be resolved. Figure 1.1 shows a sample Nessus Security Scanner report for a large network with multiple vulnerabilites on multiple hosts.

Figure 1.1 Sample Nessus Report, Nessus Client

Why a Vulnerability Assessment?

Vulnerability assessments have become a critical component of many organizations’ security infrastructures; the ability to perform a networkwide security snapshot supports a number of security and administrative processes. When a new vulnerability is discovered, the network administrator can perform an assessment, discover which systems are vulnerable, and start the patch installation process. After the fixes are in place, another assessment can be run to verify that the vulnerabilities were actually resolved.

This cycle of assess, patch, and verify has become the standard method for many organizations to manage their security issues. In fact, many are required, by an outside oversight group, to perform regular assessments of the network. Organizations must be able to show that the ongoing requirements of information security are being addressed in a timely manner. An organization can perform vulnerability assessments at regular intervals and have trend reports showing that exposed services are continually being addressed via patches until the vulnerability is no longer a threat.

Quite a few organizations have integrated vulnerability assessments into their system rollout process. Before a new server is installed, it first must go through a vulnerability assessment and pass with flying colors. This process is especially important for organizations that use a standard build image for each system; all too often, a new server can be imaged, configured, and installed without the administrator remembering to install the latest system patches. Additionally, many vulnerabilities can only be resolved through manual configuration changes; even an automated patch installation might not be enough to secure a newly imaged system.

Unlike many other security solutions, vulnerability assessments can actually assist with day-to-day system administration tasks. Although the primary purpose of an assessment is to detect vulnerabilities, the assessment report can also be used as an inventory of the systems on the network and the services they expose. Assessment reports are often used to generate task lists for the system administration staff, allowing them to prevent a worm outbreak before it reaches critical mass.

Asset classification is one of the most common non-security uses for vulnerability assessment tools. Knowing how many and what types of printers are in use will help resource planning. Determining how many Windows 2000 systems still need to be patched can be as easy as looking at your latest report. The ability to quickly glance at a document and determine what network resources might be overtaxed and those that are not being used efficiently can be invaluable to topology planning.

Assessment tools are also capable of detecting corporate policy violations; many tools will report peer-to-peer services, shared directories of copyright protected materials, and unauthorized remote access tools. If a long-time system administrator leaves the company, an assessment tool can be used to verify that a backdoor was not left in the firewall. If band-width use suddenly spikes, a vulnerability assessment can be used to locate workstations that have installed file-sharing software.

One of the most important uses for vulnerability assessment data is event correlation; if an intrusion does occur, a recent assessment report allows the security administrator to determine how it occurred and what other assets might have been compromised. If the intruder gained access to a network consisting of unpatched Web servers, it is safe to assume that he gained access to those systems as well.

Notes from the Underground…

Intrusion Detection Systems

One of the most common questions asked by people first learning about vulnerability assessments is how they differ from an IDS. To understand the differences between these complimentary security systems, you will also need to understand how an IDS works. When people speak of IDSs, they are often referring to what is more specifically known as a network intrusion detection system (NIDS). A NIDS’ role is to monitor all network traffic, pick out malicious attacks from the normal data, and send out alerts when an attack is detected. This type of defense is known as a reactive security measure; it can only provide you with information after an attack has occurred. In contrast, a vulnerability assessment provides you with the data you need before the attack happens, allowing you to fix the problem and prevent the intrusion. For this reason, vulnerability assessments are considered a proactive security measure.

Assessment Types

The term vulnerability assessment is used to refer to many different types and levels of service. A host assessment normally refers to a security analysis against a single system, from that system, often using specialized tools and an administrative user account. In contrast, a network assessment is used to test an entire...

Produkt-Details

• Erscheint lt. Verlag: 12.1.1999
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Festkörperphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Optik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Quantenphysik
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• ISBN-10: 0-08-054092-9 / 0080540929
• ISBN-13: 978-0-08-054092-4 / 9780080540924