```ts
/**
 * Returns the furthest forward position reached during a walk following a series of moves.
 * @param moves - A string containing 'F' for forward and 'B' for backward steps.
 * @returns The furthest forward position reached.
 */
export function stepBack(moves: string): number {
    let position = 0;
    let maxPosition = 0;

    for (const move of moves) {
        if (move === 'F') {
            position++;
            maxPosition = Math.max(maxPosition, position);
        } else if (move === 'B') {
            position--;
        }
    }

    return maxPosition;
}
```