Rumored Islamist "black flag"

[alarob]

I'm learning that people who are alarmed about Islamic extremism believe in a "black flag" or "flag of jihad" that bears the shadada in white calligraphic script on a black field, and is a symbol of the supposedly unified jihadi movement. I suspect that this is an urban legend based on the historical black and white flags of the Islamic caliphate, described at http://flagspot.net/flags/isl-khil.html. However, I can imagine how present-day extremists might have appropriated those flags and given them a new significance. Has anyone here encountered evidence for this?

[johnfloyd6675]

(According to Wikipedia,) Islamists use a white flag with a black Shahada as the flag of the Caliphate / "House of Peace" and a black flag with white script as the flag of Jihad. I don't know if the relationship between the flag's colors and its significance is accurate, but there are plenty of pictures online of Islamic movements with such flags.

[Mangerona]

According to the previous post, I think that, as the flag of the "house of piece" is white with black Shahada, their flag is black with black Shahada, as if they were the opposite of the "house of peace".