TCP/IP, xp questions

I hope someone can answer my basic questions....

What is a header checksum?
Is the XP firewall and Remote Assistant safe?
Is it possible to change the date/time a file is accessed after accessing it (windows or linux)?

When attempting to compile my program the thought crossed my mind that maybe something isn't in my search path. How do I do that?

I've been reading a book on TCP/IP. How crucial is it to learn the sizes of each part of an IP header and so forth?

Is VB good for anything? I know COBOL isn't.

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What is a header checksum?

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This stuff is scary for me to even attempt to go into detail with. Basically it's computed by transaction for every packet going to a destination. I need to look it back up and find out more because God knows it confuses the crap out of me.

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Is the XP firewall and Remote Assistant safe?

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Dude, you just put XP products and the word 'safe' in the same sentence! Bad! I don't know if it is or isn't...just that I know I won't ever use XP because of it's admitted "security flaws".

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Is it possible to change the date/time a file is accessed after accessing it (windows or linux)?

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For linux/unix, yes, but it's by no means an easy thing to do, even for those that could be considered "hackers". Generally, it's for a bad reason anyways, so I wouldn't worry too much about it. As for windows, who cares? MS ****s up **** enough on it's own, much less someone changing atime/mtime/ctime shite, hehe..

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When attempting to compile my program the thought crossed my mind that maybe something isn't in my search path. How do I do that?

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If you're talking about linux, do this as root:
find / -name file_name_here

Then do this:
export PATH=$PATH:/path/to/whatever/you/just/found

As for windows, find the directory, and then go into C:\autoexec.bat and edit it, adding this:

set PATH=%PATH%;absolute_path_here_including_drive_letter

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I've been reading a book on TCP/IP. How crucial is it to learn the sizes of each part of an IP header and so forth?

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Unless you're planning on going into packet-level networking and such, knowing that kind of stuff really isn't critical to know (in reference to regular sysadmin stuff)

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Is VB good for anything? I know COBOL isn't. [/B]

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VB is the mainstay of MS. Know it and you'll be able to see how they make everything in windows, as well as understanding how people make all this **** that breaks windows and whatnot. It's also the mainstay for script kiddiots, because God knows they can't do anything else other than point-and-click, possibly extending to IRC bots and running a compiler after reading the README which invariably states that the program came from somewhere like here or rootshell.org or some such place. It's decent to know, but nothing to really put on a resume (then again, since when is MS anything worthwhile? Paper MCSE anyone?)

Just my opinion on some of this stuff but hopefully it helps to a degree.

if im not mistaken the checksum is a value assigned to a packet based on the sum of its contents. on receiving a packet the checksum is compared to the actual value to see if it made the trip intact, if the packet has been corupted a request is made to resend.


IMO the xp firewall is the number one target of hackers around the world. some one will find a way to compromise it.

there's nothing more i can add about the path statment Vorlin said it all.

Their is souce code for vb apps on the net, to change the date/time property. its not something you can do without additional software.

Visual Basic is great for makeing apps on you own computer but its not very portable. unless someone has vb installed on their computer a distribution has to be made and a simple app turns into many megs. The programs also run rather slow, which isn't a problem on todays computers. its easy to use with a short learning period, you can check your program as you go, without compiling but it dosn't help you understand any other programming language.

I believe that the checksum is a value that is computed by using some obscure equation on the size of the header and stuff.

ANYWAY, the sending computer figures out the checksum of a packet, and includes said checksum with the packet when it sends. The receiving computer then calculates the checksum itself on the packet when it arrives and compares it to the checksum that it received. If they are different, the packet has been corrupted, and it is discarded.

Or something to that effect ;)

Checksum .- a method of error detection in which each transmitted message is acompanied by a numerical value based on the numbers of "1" or "0" bits in the message

I think so....

by √ÊŁØ©ïR@ρŦðب

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I free of all the perjudices. I hate averyone equally. ---w.c---Fields

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Owen76,

As for the firewall in XP being safe...I wouldn't count on it. In my opinion, a third party personal firewall (ie. ZoneAlarm or Tiny Personal Firewall) would be a better choice, or even better yet, a hardware firewall. Linksys sells a great 4-port router/switch for about $75 - $110 depending on where you shop. A good rule of thumb to remember is that while M$ products are okay to use (I can feel the heat of the flames already........) their "security features" are less than adequate. M$ is notorious for security holes, bugs, etc. I have an XP partition on my box and to tell you the truth I haven't even bothered with the XP provided firewall. Before I even dialed in to my ISP I had a third-party firewall set up and rules in place. Just my 2 cents though.....

-The Eeshman

Owen76:

A TCP header checksum is a value that is computed based on the information given in the header of the TCP packet. This checksum is used to check the integrity of the information contained in the header and can be used to recreate any missing information. If you want to know exactly what the process for creating a checksum is (this will involve semi-high level math) then let me know.

I have heard many bad things about XP's built-in firewall. I would suggest that you get Tiny Personal Firewall, or perhaps ZoneAlarm for your personal firewall needs. If you are looking for a more serious firewall, you might think about a Cable/DSL router from D-link, or Netgear.

Yes, it is possible to change the date/time accessed. In Windows, all you have to do is change the system time and click on the file and it will change to whatever the system time is at that moment.

I see that the search path question has been thoroughly taken care of, so I will forgo that.

I believe that if you have a general understanding of how a TCP packet header is put together, then you should be ok. There is certainly no need to remember the actual size of each header area. Normally, anything that requires a lot of effort to memorize isn't worth memorizing because you will almost always have the opportunity to look it up when you really need it.

Yes, VB is good for plenty of things. First, it is a simple language to learn, and some very useful/powerful programs can be made in a very short amount of time. Second, it allows for much quicker Windows user interface prototyping than any other programming language. Just because some Linux nuts are VERY anti-Windows doesn't mean that a language that works only in Windows is worthless (Note: Personally, I'm very indescriminant on my OS useage, though I absolutely HATE Windows XP).

Regards,
Wizeman

Could someone explain what a *nix system is?
I have to use a mainframe for school to compile programs.
Could someone give some commands? The only one I know is dir and that kinda sucks. It has the $ prompt.
Thank you.

Why is it called windows if the window is never open?

Owen,

A *nix system is a generic name for any one of a dozen or so flavors of Unix/Linux.

Commands for what? Compiling? Or just general sysem commands? You need to be more specific.



AFAIK XP's firewall only blocks inbound traffic. If you get a trojan or something like that, XP's firewall will not block it from sending outbound traffic. Follow the other suggestions in this thread and get ZoneAlarm or TinyPersonal Firewall. I have had great luck with the Linksys router's firewall functions personally. Its real easy to set up and have never had an intrusion while its been in operation.
HtH

L

sorry, general moving through file structure. Basic commands for displaying info and importing/exportinf files.