TweetFollow Us on Twitter

Mac OS X Security Volume Number: 17 (2001)
Issue Number: 4
Column Tag: Mac Security

Mac OS X Security

By Jesse Corbeil, Montréal Québec

Securing a Mac OS X workstation for stand-alone or home use out of the box

Note: Mac OS X is currently in Public Beta. The final version may invalidate any or all of this paper. That's just a chance we take when we write how-tos about beta operating systems

In the world of operating systems, the Macintosh platform has traditionally been everybody else's secure neighbour. Not many virii or cracks affected the Mac (unless we counted cross-platform Word macros), and we were generally spared the heaps of abuse that were laid onto our Windows-using brethren. Whether this has been due to the brotherly Mac community or the simple fact that there aren't enough Mac OS computers out there to make it worthwhile is up for debate. The truth will become clear when we all trash our old Macs and buy brand-new Cubes to run Apple's swank new OS. Why is that? Because Mac OS X is nothing more than a shiny interface on top of a tweaked BSD core, and BSD is very much slugging it out at the centre of the cracks and exploits blattleground. With that in mind, this article will discuss how to secure the default installation for a workstation or for home use.

BSD

Unix-cowboys have it all over us Mac users. They trade in the ease-of-use and smooth operation to which we are accustomed on the Mac side for raw, unlimited power over their machines. The easy Mac or Windows click-to-install approach is shunned in favour of the ability to tweak the code of an app that didn't install properly; cutting, thwacking, and generally forcing the code until the app clicks smoothly into place. Further, whereas we tend to troubleshoot by twiddling the knobs and banging the pipes, Unix-gurus crawl under the sink to pull the works apart. They know their machines better than we know our mothers.

Now, all that is about to change- at least for those of us who actually want to dig about under the hood and still enjoy the Mac OS experience.

With the change to Mac OS X, Apple reduces the number of major-player non-Unix OSes by one, while simaultaneously giving the Unix world something it has been trying to develop with imperfect solutions like KDE and Gnome: a distro with a polished and usable GUI.

What the BSD core (fetchingly called 'Darwin') gives back to the Mac is a rock-solid OS with all the buzz-technologies incorporated: multi-this, protected-that, and the new-to-Mac concept of an application crashing without taking down the OS. Unfortunately, what else we get is a security headache. Suddenly, all those Unix-savvy hacks and virii are mac-savvy too. Added to that (and I feel safe in going out on this particular limb), the country-bumpkin image that the Mac OS has enjoyed in hacker circles is about to be replaced by a perception of the OS as the sexy new Unix. Eager crackers will want to try out all the exploits and probe the nooks and crannies.

The Swiss-Cheese OS

Once they've been properly set up, the BSDs are generally pretty secure. They are developed by security-conscious communities and tend to be deployed in sensitive areas like networking and databasing. The Calgary-based OpenBSD is regarded as the most secure BSD distribution, incorporating many crypto and security features that would be non-exportable had it been an American distro subject to US export laws. Obviously, Apple could not have based Mac OS X in Open BSD and still sold the OS outside the US, but the more freely-exportable BSDs are still very secure, and the choice to base Mac OS X on the platform is still a solid one.

OpenBSD aside, any distro must be properly hardened to close up some of the dozens of holes left open by a default installation. This is where Darwin shows its BSD roots, and where a certain familiarity with Unix system hardening comes in. On a typical BSD system, one of the things an admin would do to secure the system is to edit the inetd.conf file to disable unneeded services. Mac OS X comes with the inetd.conf file already set up in a pretty secure configuration, but that doesn't mean that the OS is completely tight. There are other security holes in the default setup (such as services not covered by inetd.conf) that must be addressed before deploying the OS in a secured environment. When configuring services, the general rule of thumb is If you're not using it, turn it off.

There are some cool gewgaws in Mac OS X, though their default configurations can be pretty insecure. Running dmesg, for instance, reveals that there is an IP packet filter initialised but that it's wide open; The NFS daemon is active by default, which opens up a security hole, as does the Portmap daemon. There's an NTP daemon enabled, which opens a very slight security risk: though one wouldn't generally try to compromise the system through NTP, it is theoretically possible to muck about with it to make time-sensitive apps do one's bidding. But by far the coolest feature of the OS in terms of un-fubar-ability is the separation of admin accounts from the central, all-powerful root user. As part of the OS installation, I was asked to create an administrator account for myself. I set the system up as "jcorbeil," which is the account I generally use. From there I can administer just about anything on the machine - so long as the function is GUI accessible. However, if I try to enter rm -rf * in a Terminal window, the system will tell me to stuff myself. Why is this? It's due to Apple's approach to Mac OSX's design. Apple has made it as difficult as possible to hose your system by limiting GUI access to most of the really dangerous functions. That's a smart move on Apple's part, as it effectively stops non-gurus from inadvertently committing atrocities.

Another safety feature was revealed when I checked out the NetInfo application, which is where all system and user information is centralised. I discovered (and verified via a quick etc/passwd check) that even though my account is an administrator account, the system still pledges its allegiance to a separate root account that was automatically generated during installation. In other words, "jcorbeil" may be the system admin, but he doesn't have the same set of priviledges as the bonafide root user. To do something that only the root can (like erase the works), I have to su to root in Terminal, then do my damage. It's not hard, as the root account shares jcorbeil's password by default, but there's a certain level of know-how involved in getting to the 'destroy-the-OS' point that is beyond the ken of most new users coming from a classic Mac OS background.

Openings and Closings

To get a bit of an aperçu of what ports are open on your system, open a Terminal window and enter netstat -an (Figure 1). This will display your machine's ports and whether they are listening, established, or closed. If you want to see the ports' names, use the netstat -a command. It's a safe bet that you'll find ports you don't recognise. That's normal, but for for those who want to know all about ports, http://www.doshelp.com/trojanports.htm has some resources for the inquisutive firewall admin.


Figure 1. What comes up when you type netstat -an

Chances are, you'll find two local addresses near the bottom of the list, called *.111 and *.514. These are our first two security issues. *.111 is portmap, which is a daemon for making RPC calls. It is also lousy for security, and is best turned off. *.514 is the syslog daemon, which listens on UDP and receives log broadcasts from other servers. Sounds pretty innocuous, right? Well, UDP is not a two-way protocol, so there's no way for syslog to verify whether or not the sender of a given datum is who he says he is, which opens up the potential for a denial of service attack. Nasty stuff. Tighten *.514 up by using IPF to stop connections other than 127.0.0.1 (more on this later).

After that, run a search for any files that are either world-writeable or owned by the "nobody" user or group. Every one of these opens up a little security hole, and should therefore be viewed with great circumspection. You might need a couple of them, you might not. Look about and clean up what you can by tightening up the access control to world-writeable files or files with 'nobody' ownership.

IPFilter: Built-in Security

IPFilter is a firewall that gets installed with the kernel, and is where some of the power of a BSD-based OS comes to the fore. IPFilter alone warrants a book or two, but there are some basics that everyone can use as a springboard to using IPF fairly quickly.

IPF works by processing a rules file. The rules file is a text file of conditions and actions for IPF to take when those conditions come to pass, for example blocking packets, letting packets through, and logging them. Set up IPF's rules file for blocking, passing, and logging based upon the criteria you want to employ. For example, say you don't want TCP packets coming in. You would edit the ipf.rules file by entering the following line of text:

block in on ed0 proto tcp from any to any

If you wanted the above to block only one port (say *.514), you would change the text to read:

block in on ed0 proto tcp from any to any port = 514.

Fiddle with the file, blocking and unblocking ports until you have a tight system from which you can still run the transactions you need. It is generally a good idea to start off your rules file with a command to block all ports. That way, any port that doesn't have a rule expressly attributed to it is covered by the first rule, and is blocked.

IPF is quite powerful, and it's a good idea to become well-acquainted with it. More in-depth information can be found at http://coombs.anu.edu.au/ipfilter.

SSH and Kerberos

Two things that I haven't touched on in this article are SSH and Kerberos. That has been done on purpose, as there is very little to be done with either of them for a home or standalone system set-up. SSH comes as part of the standard installation and is an extremely effective tool for keeping your system tight. For our purposes, you won't need to change the configuration. Just be serene in the knowledge that it's running and it has your safety in mind. Accordingly, you don't need to run services like rsh, telnet, rlogin, or ftp. They represent unneeded security risks, so unless you expressly need one of them for something, shut them down.

Kerberos uses a client/server setup, and you would only worry about Kerberos if you were on a network that uses the protocol. Since we're securing a home machine, we'll leave Kerberos alone.

Take it to the Bone

These solutions are not the be-all, end-all secret to how to secure your home system from a brilliant hacker, but they do form a solid foundation from which you can do further research into the methods and tools available to secure your computer. If you want to read further, check out the IP FilterFAQ at http://coombs.anu.edu.au/ipfilter/ipfilfaq.html, or read O'Reilly's Practical UNIX & Internet Security by Garfinkel and Spafford.

Whether or not you decide to delve into the deep, dark depths of computer security, a basic knowledge will still help you understand the basics. Basic knowledge will at least let you understand the theory behind a security breach that might nail your machine, and understanding will hand you the keys you need to get the problem fixed. Computer security doesn't have to be scary, indeed, it can even sometimes be fun. Getting caught unawares by a cracker, on the other hand, can cause you immeasurable pain.


Jesse Corbeil is the Director of Documentation at SecureOps, a network security consulting firm in Montréal, Canada. He has written for beoscentral.com and several other information sites, and is involved in the Marathon Open Source project.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

calibre 2.17 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
OmniGraffle Pro 6.1.2 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.1.2 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
RoboForm 2.0.2 - Password manager; syncs...
RoboForm is a password manager that offers one-click login, mobile syncing, easy form filling, and reliable security. Password Manager. RoboForm remembers your passwords so you don't have to! Just... Read more
Apple MainStage 3.1 - Live performance t...
Love the sound you got on your recording? MainStage 3 makes it easy to bring all the same instruments and effects to the stage. Everything from the Sound Library and Smart Controls you're familiar... Read more
Freeway Pro 7.0.2 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
A Better Finder Rename 9.44 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
Stacks 2.6.9 - New way to create pages i...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
Sid Meier's Civilization: Beyond Ea...
Sid Meier's Civilization: Beyond Earth is a new science-fiction-themed entry into the award-winning Civilization series. Set in the future, global events have destabilized the world leading to a... Read more
Logic Pro X 10.1 - Music creation and au...
Apple Logic Pro X is the most advanced version of Logic ever. Sophisticated new tools for professional songwriting, editing, and mixing are built around a modern interface that's designed to get... Read more

Choice Provisions is Set to Launch Destr...
Choice Provisions is Set to Launch Destructamundo on iOS This Month Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] Choice Provisions – home stable to | Read more »
King of Thieves – An Interview With Zept...
Ahead of the release of ZeptoLab’s King of Thieves, we were able to ask ZeptoLab’s co-founder, Semyon Voinov, a few questions about the inspiration behind the game and what that means for the Cut the Rope franchise. | Read more »
Handle Review
Handle Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: SPEEDY ORGANIZINGUniversal App - Designed for iPhone and iPad Handle is a very convenient way of juggling your emails, To Do list, and Calendar all through one... | Read more »
The New Disney Inquizitive App Offers a...
The New Disney Inquizitive App Offers a Place for Fans to Take Disney Quizzes Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] | Read more »
Hands-On With Cut the Rope Developer Zep...
Marking quite a departure from ZeptoLab’s past successes, namely the Cut The Rope series, King of Thieves is shaping up to be quite promising. Due for release in February, we were lucky enough to have some time with a preview build to see exactly... | Read more »
Fast Fishing Review
Fast Fishing Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: LIVES UP TO ITS NAMEUniversal App - Designed for iPhone and iPad Fishing is far from relaxing in Fast Fishing, but it is fun.   | Read more »
The LEGO Movie Video Game is Available N...
The LEGO Movie Video Game is Available Now for iOS Posted by Ellis Spice on January 23rd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Satellina Review
Satellina Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: TWITCHY BUT TACTICALUniversal App - Designed for iPhone and iPad Satellina requires quick thinking and twitchy fingers, and it’s pretty fun.   | Read more »
Tail Drift, the Crazy 360 Degree Flyer,...
Tail Drift, the Crazy 360 Degree Flyer, Has Gone Free-to-Play in a New Update Posted by Jessica Fisher on January 22nd, 2015 [ permalink ] | Read more »
PureSkate 2 Review
PureSkate 2 Review By Tre Lawrence on January 22nd, 2015 Our Rating: :: ALMOST ALL AIRUniversal App - Designed for iPhone and iPad PureSkate 2 lets one’s fingers do the skateboarding.   | Read more »

Price Scanner via MacPrices.net

College Student Deals are back, additional $5...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through April 11, 2015. Anyone with a valid .EDU email address can take advantage... Read more
iPhone 6 and 6 Plus GIve Apple Half Of US Mob...
Chicago-based Consumer Intelligence Research Partners, LLC (CIRP) have released analysis of the results of its research on mobile phone manufacturers for the calendar quarter that ended December 31,... Read more
Save $100 on MacBook Airs with 256GB of stora...
B&H Photo has 256GB MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.4GHz/256GB MacBook Air: $999 $100 off MSRP - 13″ 1.4GHz/256GB MacBook... Read more
21-inch 2.7GHz iMac on sale for $1179, save $...
B&H Photo has the 21″ 2.7GHz iMac on sale for $1179 including free shipping plus NY sales tax only. Their price is $120 off MSRP, and it’s the lowest price available for this model from any... Read more
iPhone Usage Rates by State Correlate With Ed...
Chitika Insights notes that despite iPhones being the largest source of smartphone Internet traffic in North America, their latest study finds a relatively high degree of variation of iPhone usage... Read more
ProGearX Extendable Pole “Pov/Selfie Stick” M...
There’s something inescapably narcissistic about the concept of selfies as they’ve developed as a smartphone-driven social (particularly social media) phenomenon that rubs me the wrong way. However,... Read more
iPad Air 2 on sale for up to $100 off MSRP, 2...
 Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for the next two days. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Roundup of Apple refurbished MacBook Pros and...
The Apple Store has Apple Certified Refurbished 2014 MacBook Pros and MacBook Airs available for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Sale! 13-inch 2.8GHz Retina MacBook Pro for $...
 B&H Photo has the 13″ 2.8GHz Retina MacBook Pro on sale for $1599 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model... Read more
Next OS X/iOS Version Upgrades Should Concent...
On stage at Apple’s World Wide Developers’ Conference in June 2009, Bertrand Serlet, the company’s Senior Vice President of Software Engineering at the time, announced that the forthcoming OS X... Read more

Jobs Board

*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Lead Operator, GSOC - Apple (United...
**Job Summary** Apple is seeking an exceptional, customer service oriented and experienced persons to fulfill the role of Apple Lead Operator (ALO) as part of the Read more
Order Support Supervisor- *Apple* Online Sto...
**Job Summary** The Apple Online Store (AOS) Order Administration team is looking for an Order Support Supervisor to manage and lead a team of Specialists through the Read more
Senior Program Manager, *Apple* Online Supp...
**Job Summary** The Apple Online Support Planning team is looking for an experienced Senior Project Manager to lead key Quality program initiatives across the Online Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.