Computer Tips -Tech Info

I remember many years ago watching a Dr. Who episode where a very important key was “hidden” in a display of many other keys. Kind of like hiding a tree in a forest. This concept is “security by obscurity”. Generally this is considered a bad approach to security. It is a bad approach if this is the ONLY thing you consider. Many examples are security by obscurity are usually thought of as… proprietary applications that keep source code secret so no one can find what flaws exist, using operating systems or programs that are “obscure” or have small market share and are not targetted.

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Let me start by saying I am FAR from being an expert on the subject of building rpm’s… RPM’s are binary packages for use in red-hat based distributions. They are used (*in my case on Mandriva) with urpmi to install. Urpmi is a “wrapper” around the rpm utility that figures out what dependencies a program has and then installs those dependencies along with that program. One problem under linux is that binaries are not necessarily portable from one version of a distribution to another. For instance, some of the rpm’s for cooker may not be compatible with an old 10.0 system. But, there are src.rpm’s that can be rebuilt.

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I remember back when I was running Windows as my primary OS, one of my favorite diversions was Microsoft Flight Simulator (2000?) In fact, I clearly remember circumnavigating the globe in a Cessna in that program (landing at a small strip in Icelend, the old Hong Kong International airport and some airstrip in the Himalayas were the most challenging. In fact, for the altitude problems I didn’t think I’d make it past the himalayas…) Anyway, when I moved to linux it wouldn’t run under wine and there wasn’t much out there to compare that ran under linux.

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Ok – so now post upgrade to Mandriva 2006 I sit down to try something out. Put a dvd in the drive and see what happens. I rarely sit and watch dvd’s on the desktop, but it’s always been a possibility… So, when I pop the disc in, kaffeine pops up with it’s “install” sequence – checks to see what’s on the system and what’s not what version of kde, libdvdcss, dvd, dvb hardware, etc….

So, the disc pops up and no sound…. hmm. maybe it’s just kaffeine…

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I’m going to do a few articles on building RPM’s as much for my own reference as anyone elses. I’m not an expert on the subject by any means… I do this from time to time, rebuild an rpm for an older system (or even a newer system that doesn’t have an official rpm for.) I have a tendency to forget things that I don’t do frequently. The first part of being able to rebuild rpm’s is to have what’s called a build environment. For starters, I’m using Mandriva 2006 (older versions I used Mandrake 10.1 or 10.0, etc.) In your home directory you need a folder called rpm.

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I’ll confess to having a lot to learn about IP ethernet networking. I feel pretty comfortable with basic TCP/IP (v4), the concept of UDP vs. TCP ports, ICMP pings, etc… but ARP is something that I haven’t dabbled much with. It is, of course, a layer that TCP depends on. When a machine sends a packet to another machine, it sends an arp packet out to “discover” the hardware (MAC) address of the machine on the other end, so ARP underlies everything. These days ICMP is many times blocked by firewall rules. The default with XP’s software firewall is to block ICMP pings for instance.

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There are ways that risks can be avoided. Recently, there was what was called a zero-day exploit for Internet Explorer. As I write this, the exploit surfaced 3 weeks ago and tomorrow there will be a patch. The vulnerability would allow remote code execution through a vulnerability in the way javascript is handled. So, for that 3 week unpatched period, Internet Explorer in it’s default configuration is a sitting duck. Well, truth be told, there are other browser vulnerabilities, many unpatched. (That’s a common method for many spyware bugs to install.)

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OK – so as I have mentioned after upgrading to Mandriva 2006 I was looking at the possibility of moving from Evolution to Kontact as the main mail client. I moved contacts and got things massaged quite well. One of the neat features in Kontact is the ability to have multiple address-books/resource names. Anyway, I moved on to calendar items which given that some of what I do is recurring appointments is fairly easy to reconstruct if necessary. Anyway, I got those copied over and thought I’d take advantage of being able to use different calendar files to organize different things. For instance I thought – why don’t I do a seperate file for Holidays…

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I REALLY like secure shell (SSH) for remote access to linux machines. You can do more than just a “telnet” like remote shell with it. (Port forwarding.) However, the default configuraton for the openssh-server is sometimes a bit less tight than I would like. For that reason on a new install, I usually like to make a few changes. I don’t know if I’ve mentioned this before, but I haven’t devoted a post JUST to this, so… here we go.

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There’s a joke that many people bring out when new Windows viruses hit big…. it goes along the lines of, “download a fix here” and the link points to a knoppix linux livecd download, or a Mandriva download disk, fedora/etc… Some say linux isn’t affected by as many viruses because it lacks market share, I would point out that server market share (take a look at how many linux web servers there are…) would seem to tip the scales a bit, but that’s not the point of this post. What is the point is this…. When you have a Windows pc that is infested what you should do is disconnect from the internet. The problem is, that typically prevents you from getting the tools you need to fix the machine.

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