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

Artlantis Studio 5.1.2.7 - 3D rendering...
Artlantis Studio is a unique and ideal tool for performing very high resolution rendering easily and in real time. The new FastRadiosity engine now lets you compute images in radiosity-even in... Read more
MacUpdate Desktop 6.0.5 - Search and ins...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
BitTorrent Sync 2.0.82 - Sync files secu...
BitTorrent Sync allows you to sync unlimited files between your own devices, or share a folder with friends and family to automatically sync anything. File transfers are encrypted. Your information... Read more
Google Drive 1.20 - File backup and shar...
Google Drive is a place where you can create, share, collaborate, and keep all of your stuff. Whether you're working with a friend on a joint research project, planning a wedding with your fiancé, or... Read more
Simon 4.0.3 - Monitor changes and crashe...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
Vitamin-R 2.23 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
iDefrag 5.0.0 - Disk defragmentation and...
iDefrag helps defragment and optimize your disk for improved performance. Features include: Supports HFS and HFS+ (Mac OS Extended). Supports case sensitive and journaled filesystems. Supports... Read more
PCalc 4.2 - Full-featured scientific cal...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
FileZilla 3.10.2 - Fast and reliable FTP...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.10.2: Note: Now requires a 64-bit Intel processor.... Read more
The Hit List 1.1.11 - Advanced reminder...
The Hit List manages the daily chaos of your modern life. It's easy to learn - it's as easy as making lists. And it's powerful enough to let you plan, then forget, then act when the time is right.... Read more

Protect Yourself from an Onslaught of Ca...
Surprise Attack Games has announced a Cat-astrophic new physics puzzler called Fort Meow! In the game, a young girl named Nia finds her grandfather’s journal which triggers an all mighty feline attack! Why do the cats want the journal? Who knows,... | Read more »
GDC 2015 – Jelly Reef will be Game Oven’...
GDC 2015 – Jelly Reef will be Game Oven’s Last Hurrah, and it Seems like a Good Note to Go Out on Posted by Rob Rich on March 4th, 2015 [ permalink ] It’s sad knowing that Game Oven ( | Read more »
daWindci Deluxe Review
daWindci Deluxe Review By Campbell Bird on March 4th, 2015 Our Rating: :: BLUSTERY PUZZLESUniversal App - Designed for iPhone and iPad This updated puzzle game offers some creative gameplay and new mechanics, but still suffers from... | Read more »
Dungeon Hunter 5 Coming on March 12
Gameloft has excitedly announced that Dungeon Hunter 5 is on its way! Once again, you will adventure across the land of Valenthia exploring dungeons and fighting monsters. The game will have a new asynchronous multiplayer mode called Strongholds... | Read more »
GDC 2015 – The Sandbox 2 is Coming, and...
GDC 2015 – The Sandbox 2 is Coming, and Now it has Textures! | Read more »
Warner Bros. Interactive Announces Mort...
Mortal Kombat X, by Warner Bros. and NetherRealm Studios, will be a a free-to-play fighting/card-battle Mortal Kombat game. The game promises card collecting, multiplayer team combat, classic characters such as Scorpion, Sub-Zero and Raiden, and the... | Read more »
GDC 2015 – Piloteer is Whitaker Trebella...
GDC 2015 – Piloteer is Whitaker Trebella’s Latest Project, and it’s Definitely Something DIfferent Posted by Rob Rich on March 3rd, 2015 [ permalink ] You know | Read more »
PangoLand Review
PangoLand Review By Amy Solomon on March 3rd, 2015 Our Rating: :: COME VISIT PANGO AND FRIENDSUniversal App - Designed for iPhone and iPad PangoLand is an open-ended world full of familiar characters, bright colors and interactive... | Read more »
Knights of Pen & Paper is Leveling U...
With the roll of a die and a critical success, Paradox Interactive has announced Knights of Pen & Paper 2! You’ll be taking your place at the table once again in this sequel to Knights of Pen & Paper +1 Edition. The game will introduce the... | Read more »
GDC 2015 – Project Highrise is an Intere...
GDC 2015 – Project Highrise is an Interesting Idea from SomaSim Posted by Rob Rich on March 3rd, 2015 [ permalink ] You might know SomaSim best from their gold rush sim, 1849< | Read more »

Price Scanner via MacPrices.net

Mac Pros on sale for up to $279 off MSRP
Amazon has Mac Pros in stock and on sale for up to $279 off MSRP. Shipping is free: - 4-Core Mac Pro: $2725.87, $273 off MSRP (9%) - 6-Core Mac Pro: $3719.99, $279 off MSRP (7%) Read more
Sale! 13-inch Retina MacBook Pros for up to $...
B&H Photo has 13″ Retina MacBook Pros on sale for up to $205 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.6GHz/128GB Retina MacBook Pro: $1219.99 save $80 - 13″ 2.... Read more
Another Tranche Of IBM MobileFirst For iOS Ap...
IBM has announced the next expansion phase for  its IBM MobileFirst for iOS portfolio, with a troika of new apps to address key priorities for the Banking and Financial Services, Airline and Retail... Read more
Sale! 15-inch Retina MacBook Pros for up to $...
B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for up to $250 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $... Read more
WaterField Designs Introduces the Minimalist...
With Apple Pay gaining popularity, Android Pay coming in May 2015, and loyalty cards and receipts that can be accessed from smartphones, San Francisco’s WaterField Designs observes that it may be... Read more
Sale! 15-inch 2.2GHz Retina MacBook Pro for $...
 Best Buy has the 15″ 2.2GHz Retina MacBook Pro on sale for $1774.99 $1799.99, or $225 off MSRP. Choose free home shipping or free local store pickup (if available). Price valid for online orders... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $170 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for... Read more
Apple Launches Free Web-Based Pages and Other...
Apple’s new Web-only access to iWork productivity apps is a free level of iCloud service available to anyone, including people who don’t own or use Apple devices. The service includes access to Apple... Read more

Jobs Board

*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
Position Opening at *Apple* - Apple (United...
…Summary** As a Specialist, you help create the energy and excitement around Apple products, providing the right solutions and getting products into customers' hands. You Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** The Apple Store is a retail environment like no other - uniquely focused on delivering amazing customer experiences. As an Expert, you introduce people 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* Pay Automation Engineer - iOS System...
**Job Summary** At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring passion and dedication to your job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.