what does 'b.jpg?xxxx' mean? is it a jpg or a script?

[leo.hou]

Dear experts,

I came across the following script in a htm file. Could some one
explain why is it passing some parameter to a jpg file? What does it
mean?

Thanks

<script language="JavaS cript" type="text/javascript">
<!--
var r=Math.random() ;
document.write( "<img alt=\"\" width=\"1\" height=\"1\"
style=\"display :none\" ");

document.write( "src=\"http ://tracking.xxxx.c om/b.jpg?cD0yJnU9e y9jbHViLmNoaW5h LmFsaWJhYmEuY29 tL2h0bWwvcGFnZS 9jaGF0Lmh0bWx9J m09e0dFVH0mcz17 MjAwfSZyPXtodHR wOi8vY2hhdDEuaW 5mby5jaGluYS5hb GliYWJhLmNvbS8w MS9saXZlX3RvcC5 odG1sfSZhPXstfS ZiPXtjX2Nfc2lnb mVkPU59JmM9ey19 &rand="+r+"\">" );
-->
</script>
Leo

[leo.hou]

I downloaded this b.jpg file (using flashget) and ultraedit shows the
following. (acdsee views it as a blank image). Could some one explain
what's going on? Thanks!
00000000h: FF D8 FF E0 00 10 4A 46 49 46 00 01 01 00 00 01 ;
??.JFIF..... .
00000010h: 00 01 00 00 FF FE 00 3E 43 52 45 41 54 4F 52 3A ;
.....?>CREAT OR:
00000020h: 20 67 64 2D 6A 70 65 67 20 76 32 2E 30 20 28 75 ; gd-jpeg
v2.0 (u
00000030h: 73 69 6E 67 20 49 4A 47 20 4A 50 45 47 20 76 36 ; sing IJG
JPEG v6
00000040h: 32 29 2C 20 64 65 66 61 75 6C 74 20 71 75 61 6C ; 2),
default qual
00000050h: 69 74 79 0A FF DB 00 43 00 08 06 06 07 06 05 08 ;
ity.?C...... ..
00000060h: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12 ;
............... ..
00000070h: 13 0F 14 1D 1A 1F 1E 1D 1A 1C 1C 20 24 2E 27 20 ;
............ $.'
00000080h: 22 2C 23 1C 1C 28 37 29 2C 30 31 34 34 34 1F 27 ;
",#..(7),01444. '
00000090h: 39 3D 38 32 3C 2E 33 34 32 FF DB 00 43 01 09 09 ;
9=82<.342?C. ..
000000a0h: 09 0C 0B 0C 18 0D 0D 18 32 21 1C 21 32 32 32 32 ;
.........2!.!22 22
000000b0h: 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 ;
222222222222222 2
000000c0h: 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 ;
222222222222222 2
000000d0h: 32 32 32 32 32 32 32 32 32 32 32 32 32 32 FF C0 ;
22222222222222ï £µ?
000000e0h: 00 11 08 00 01 00 01 03 01 22 00 02 11 01 03 11 ;
..........".... ..
000000f0h: 01 FF C4 00 1F 00 00 01 05 01 01 01 01 01 01 00 ;
..?......... ...
00000100h: 00 00 00 00 00 00 00 01 02 03 04 05 06 07 08 09 ;
............... ..
00000110h: 0A 0B FF C4 00 B5 10 00 02 01 03 03 02 04 03 05 ;
...??....... ..
00000120h: 05 04 04 00 00 01 7D 01 02 03 00 04 11 05 12 21 ;
.......}....... .!
00000130h: 31 41 06 13 51 61 07 22 71 14 32 81 91 A1 08 23 ;
1A..Qa."q.2亼? #
00000140h: 42 B1 C1 15 52 D1 F0 24 33 62 72 82 09 0A 16 17 ;
B绷.R佯$3br?. ..
00000150h: 18 19 1A 25 26 27 28 29 2A 34 35 36 37 38 39 3A ;
....%&'()*45678 9:
00000160h: 43 44 45 46 47 48 49 4A 53 54 55 56 57 58 59 5A ;
CDEFGHIJSTUVWXY Z
00000170h: 63 64 65 66 67 68 69 6A 73 74 75 76 77 78 79 7A ;
cdefghijstuvwxy z
00000180h: 83 84 85 86 87 88 89 8A 92 93 94 95 96 97 98 99 ;
儎厗噲墛挀 敃枟槞
00000190h: 9A A2 A3 A4 A5 A6 A7 A8 A9 AA B2 B3 B4 B5 B6 B7 ;
æ®ºï¿¥ã‚¦Ð–â”†æ ¸¤å�¹æ–—
000001a0h: B8 B9 BA C2 C3 C4 C5 C6 C7 C8 C9 CA D2 D3 D4 D5 ;
腹�媚牌侨 墒矣哉
000001b0h: D6 D7 D8 D9 DA E1 E2 E3 E4 E5 E6 E7 E8 E9 EA F1 ;
è‚¿åˆ*å�ºå¿�溴 éª�æ*�犟
000001c0h: F2 F3 F4 F5 F6 F7 F8 F9 FA FF C4 00 1F 01 00 03 ;
�趱鲼??. ...
000001d0h: 01 01 01 01 01 01 01 01 01 00 00 00 00 00 00 01 ;
............... ..
000001e0h: 02 03 04 05 06 07 08 09 0A 0B FF C4 00 B5 11 00 ;
...........? ?.
000001f0h: 02 01 02 04 04 03 04 07 05 04 04 00 01 02 77 00 ;
............... w.
00000200h: 01 02 03 11 04 05 21 31 06 12 41 51 07 61 71 13 ;
.......!1..AQ.a q.
00000210h: 22 32 81 08 14 42 91 A1 B1 C1 09 23 33 52 F0 15 ;
"2?.B憽绷.#3R ?
00000220h: 62 72 D1 0A 16 24 34 E1 25 F1 17 18 19 1A 26 27 ;
br?.$4??...&'
00000230h: 28 29 2A 35 36 37 38 39 3A 43 44 45 46 47 48 49 ;
()*56789:CDEFGH I
00000240h: 4A 53 54 55 56 57 58 59 5A 63 64 65 66 67 68 69 ;
JSTUVWXYZcdefgh i
00000250h: 6A 73 74 75 76 77 78 79 7A 82 83 84 85 86 87 88 ;
jstuvwxyz們å‰* 唶?
00000260h: 89 8A 92 93 94 95 96 97 98 99 9A A2 A3 A4 A5 A6 ;
墛挀敃枟槞 殺￥ウ
00000270h: A7 A8 A9 AA B2 B3 B4 B5 B6 B7 B8 B9 BA C2 C3 C4 ;
Ж┆渤å�¹æ–—è …¹éƒ�媚
00000280h: C5 C6 C7 C8 C9 CA D2 D3 D4 D5 D6 D7 D8 D9 DA E2 ;
牌侨墒矣哉 è‚¿åˆ*é˜�
00000290h: E3 E4 E5 E6 E7 E8 E9 EA F2 F3 F4 F5 F6 F7 F8 F9 ;
沅�玷殛� 趱鲼
000002a0h: FA FF DA 00 0C 03 01 00 02 11 03 11 00 3F 00 F9 ;
??.........?.?
000002b0h: FE 8A 28 A0 0F FF D9 ; (?
le*****@gmail.c om wrote:

Dear experts,

I came across the following script in a htm file. Could some one
explain why is it passing some parameter to a jpg file? What does it
mean?

Thanks

<script language="JavaS cript" type="text/javascript">
<!--
var r=Math.random() ;
document.write( "<img alt=\"\" width=\"1\" height=\"1\"
style=\"display :none\" ");

document.write( "src=\"http ://tracking.xxxx.c om/b.jpg?cD0yJnU9e y9jbHViLmNoaW5h LmFsaWJhYmEuY29 tL2h0bWwvcGFnZS 9jaGF0Lmh0bWx9J m09e0dFVH0mcz17 MjAwfSZyPXtodHR wOi8vY2hhdDEuaW 5mby5jaGluYS5hb GliYWJhLmNvbS8w MS9saXZlX3RvcC5 odG1sfSZhPXstfS ZiPXtjX2Nfc2lnb mVkPU59JmM9ey19 &rand="+r+"\">" );
-->
</script>
Leo

[Tom Cole]

le*****@gmail.c om wrote:

Dear experts,

I came across the following script in a htm file. Could some one
explain why is it passing some parameter to a jpg file? What does it
mean?

Thanks

<script language="JavaS cript" type="text/javascript">
<!--
var r=Math.random() ;
document.write( "<img alt=\"\" width=\"1\" height=\"1\"
style=\"display :none\" ");

document.write( "src=\"http ://tracking.xxxx.c om/b.jpg?cD0yJnU9e y9jbHViLmNoaW5h LmFsaWJhYmEuY29 tL2h0bWwvcGFnZS 9jaGF0Lmh0bWx9J m09e0dFVH0mcz17 MjAwfSZyPXtodHR wOi8vY2hhdDEuaW 5mby5jaGluYS5hb GliYWJhLmNvbS8w MS9saXZlX3RvcC5 odG1sfSZhPXstfS ZiPXtjX2Nfc2lnb mVkPU59JmM9ey19 &rand="+r+"\">" );
-->
</script>

While I can't comment on this particular instance, when I write these,
it points to server side code (in my case servlets) that are generating
the images on the fly (for a captcha, for example).
There is no rule that a resource with an extension .jpg or the src
attribute of an image has to point to an image file, only it should
point to something that returns image data.

HTH.

>
Leo

[Andy Dingley]

le*****@gmail.c om wrote:

I came across the following script in a htm file. Could some one
explain why is it passing some parameter to a jpg file?

"tracking.c om" is the clue

It's a web bug, a single pixel transparent GIF. There's no need to
involve a script at all, the "query parameter" is just an ID string
that will be extracted from the webserver logs afterwards. The site
hosting the image tracks many 3rd party sites and the identifiers
differ for each.

Of course it could be an image as a static file, or it could be a
server-side script that generates an image as a stream of bytes in the
HTTP response (as many web page counters use). There's simply no way
it's possible to tell - but simplicity suggests a static file.