You denizens of the Tool Bar & Grill are all wonderful folks, each and every one, with fine qualities too numerous to list. Among your best traits is the desire to learn new things every day. You are an admirably inquisitive lot.
Some people learn best by reading, others by watching. You visual learners can read on to find the best Web sites that teach new skills through video demonstrations. (For you readers, see post #70, “Guide for the Perplexed: Where To Find How-To’s,” for some great text-based instructional Web sites.)
I usually publish a new post here every Sunday. I apologize to all my faithful readers for publishing this post a bit late. It’s because this past Sunday I was busy assembling a crib for my adorable new grandson. I figured out the easy way to do it after struggling with it for quite a while. Perhaps if I had checked the Web for video tutorials, I would have finished faster!
Learn By Watching
Instructional videos have burst across the Internet like mushrooms after a rain. Some are highly professional, while others are laughably amateur. Some sites pay for good videos, and some contributors toil day and night to crank out new videos in a variety of subjects. The hard part is finding the best ones.
You probably would assume, as I did, that it’s best to start with one of the video aggregators, which collect instructional videos from many other sites all across the Web. WonderHowTo claims to be the biggest, boasting over 100,000 videos. SuTree is smaller, with over 33,000 entries. Both have a social networking flavor, relying on both members and search bots to find video tutorials, and SuTree also hosts some videos of its own. However, when I searched for “assemble crib,” both sites returned numerous results with either “assemble” or “crib,” but only one video – from About.com on crib safety – that actually mentioned crib assembly. SuTree preceded the video with an advertisement. This despite my finding a number of privately produced (but not very helpful) crib assembly videos on YouTube.
Therefore, I recommend trying some of the following broad-range instructional video sites when you’re in the mood to learn something new.
ExpertVillage claims to be the “world’s largest video how-to site,” with nearly 99,000 videos. The site uses videos only from credentialed experts, whose qualifications are listed briefly.
Howcast, relatively new in the field, specializes in professionally produced instructional videos, and also offers production tools for amateur auteurs. Specific scenes or steps are marked so you can skip right to them.
5min (“life videopedia”) presents member-submitted videos of under five minutes on specialized topics. (Complex subjects might be the subject of a series of videos.) As with all the community-based sites, quality can vary.
Instructables (“the world’s biggest show & tell”) also showcases how-to videos submitted by its members.
eHow (featured in post #70) hosts mainly text tutorials, but has been branching into video too, both professional and user-generated. The selection still is somewhat limited, compared to the larger sites.
VideoJug (“life explained on film”) primarily offers professionally produced videos (with charming British-accented narration), but also user-submitted and discussion forums.
TricksPro, another community-based site, appears to have a limited inventory compared to the more established sites, and its busy interface is a bit harder to navigate.
ViewDo is yet another community-based site, with no distinguishing features that I could detect.
Graspr appears to be distinguished only by the ability to skip directly to specific marked scenes or steps in the user-produced videos (like Howcast).
Sclipo offers both professional and user-submitted videos, but does not seem to screen out relatively amateurish productions.
I finally assembled the crib without any help. But when my grandson is older, we’ll explore the Web together to learn how to throw a boomerang, play rugby, build a computer or a dune buggy, or maybe knit a tea cozy.
Linux Firewalls, Part 2
by Mark Lautman
I once had an insurance agent who had a very effective sales technique: He would always talk about the client who died a horrible death from cancer at age 40, a young widow left penniless, orphans running in the streets begging for money from tourists. “You can avoid all that if you buy life insurance from me,” was his closing statement. That guy worked three hours a day and bought a new car every year; I work eight hours a day and drive a car made in the last century.
Scare tactics are as appropriate for computer security as they are for insurance policies. If you don’t want your domestic partner to be kicked out of his or her home after a network attack, if you don’t want your children suffering abuse in foster homes, continue reading.
In my last post, we started reviewing firewall tools for Linux. One other application worthy of mention is kmyfirewall, which runs on the KDE desktop. It is similar to Firestarter, which we discussed last week. Here is a sample of blocking outbound traffic to the Tool Bar’s Web page:
After rereading my last post, I now realize that a clarification is in order. The packages Firestarter and kmyfirewall are front ends to iptables, which is the underlying firewall program in Linux. Firestarter and kmyfirewall don’t do actual firewalling, they only help you make entries into the iptables database. You can create your own firewall in iptables directly, as we discussed in the preceding post.
Let’s dig a little deeper into what a firewall actually does. All of the traffic going through your network connection needs at least a source address (your computer’s address), a destination address, and a protocol. All these items are included in an IP header. One example of a firewall breach is when a program floods your network connection with outgoing IP headers containing a fictitious source address, that is, an address other than your own. The destination address will then start sending responses to the fictitious source address. This clogs the network connection of three victims: your computer, the destination computer, and the bogus source computer.
IP headers, along with TCP headers, carry most of the Internet traffic for Web pages and FTP transfers. IP headers contain 160 teeny-tiny bits that, if hijacked, can do an awful lot of damage. (Good illustrations of IP and TCP headers are here.) Firewalls examine the bits of every single header crossing your network connection, and allow or deny passage depending on the firewall’s rules.
A measure of a firewall’s flexibility is the number of fields it can examine inside the IP header. The standard firewall tools for Windows and Linux typically examine the basic fields: source, destination, port, and protocol. iptables goes much further than that, examining obscure fields such as “time-to-live.” The most thorough reference I found for iptables is the Iptables Tutorial. If you’re paranoid, it’s a must-read. If you’re not paranoid, you will be after you read the tutorial.
Modern firewalls for Windows have a very useful ability to “learn” filtering rules; whenever an unknown packet tries to go over the network connection, the firewall asks you for approval. The one Linux utility that has this feature is mason. Unfortunately I could not get it to work with Ubuntu, and I couldn’t find other learning firewalls. While some Linux users claim firewall rules should be designed, not learned, I would like to have this feature available.
You can compensate for the lack of firewall alerts by sniffing your own network connection. Wireshark (Windows, Mac, Linux) is the premier protocol analyzer that gives you a very clear and detailed picture of your network activity. Here is a snapshot of a recent visit to the Tool Bar:
You can review Wireshark’s reports for suspicious activity, and close your firewall’s holes as necessary.
That’s all for Linux firewalls. Next week we’ll do a short review of antivirus and antispyware tools, and then return to slightly more important topics, like the extinction of all life after the asteroid collision in 2036. –Mark Lautman
Well, dear readers, I have certainly learned enough for one week. Please come back next week for more great tips on handy Windows and Linux utilities and helpful Web sites. Feel free to share your thoughts by clicking on “comments” below or writing to email@example.com. And please help this blog survive by clicking on our advertisers’ links.