Por padrão, você está olhando para a representação binária (hexadecimal) dos dados de carga útil nos pacotes, que para o caso de tráfego da Web em texto simples seria ascii codificado
O Wireshark oferece suporte para representar os dados binários como símbolos ascii em vez de binários - isso é um detalhamento de comentários como fazer isso.
Veja um trecho da seção sobre visualização HTTP e ASCII nesse link:
If you are working with TCP based protocols it can be very helpful to see the data from a TCP stream in the way that the application layer sees it. Perhaps you are looking for passwords in a Telnet stream, or you are trying to make sense of a data stream. Maybe you just need a display filter to show only the packets of that TCP stream. If so, Wireshark’s ability to follow a TCP stream will be useful to you
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The stream content is displayed in the same sequence as it appeared on the network. Traffic from A to B is marked in red, while traffic from B to A is marked in blue. If you like, you can change these colors in the “Colors” page if the “Preferences” dialog.
Non-printable characters will be replaced by dots.
The stream content won’t be updated while doing a live capture. To get the latest content you’ll have to reopen the dialog.
You can choose from the following actions:
Save As: Save the stream data in the currently selected format.
Print: Print the stream data in the currently selected format.
Direction: Choose the stream direction to be displayed (“Entire conversation”, “data from A to B only” or “data from B to A only”).
Filter out this stream: Apply a display filter removing the current TCP stream data from the display.
Close: Close this dialog box, leaving the current display filter in effect.
You can choose to view the data in one of the following formats:ASCII: In this view you see the data from each direction in ASCII. Obviously best for ASCII based protocols, e.g. HTTP.
EBCDIC: ...