Security inks react with common eradication chemicals. These inks reduce a forger's ability to modify the printed dollar amount or alter the designated payee because when solvents are applied, a chemical reaction with the security ink distorts the appearance of the check. This makes such items very difficult to alter without detection. The chemical reactants produce permanent stains when bleach or solvents are used to alter the check document. Embedded in the sheet, fibers are visible only under ultraviolet light, and are extremely difficult to duplicate.
Fibers are visible in ordinary light and arranged on both sides of the check.
These fibers will extend from a torn edge to verify its authenticity. Use a durable color ink. If you want to use a ballpoint pen, use a Bic pen with black ink. It seems that from studies, that you should be safe using these pens. If you are a ballpoint pen lover, switch to black ink when security is important.